General EE Flashcards
The tendency of electron dipole moments to align with an applied magnetic field
Paramagnetism
If a circuit has L closed loops, B branches, and J junctions the number of independent loop equations is:
B – J + 1
It is the magnetic dipole moment per unit volume of an object
Magnetization
For any circuit the number of independent equations containing emf’s, resistances and currents equals:
the number of branches
“The sum of the currents into a junction equals to sum of the currents out of the junction” is a consequence of:
Conservation of charge
Faraday’s law states that an induced emf is proportional to:
the rate of change of the magnetic flux
It is the tendency of electron dipole moments to align with each other
Ferromagnetism
For an ohmic substance, the electron drift velocity is proportional to:
the electric field in the sample
The resistance of resistor 1 is twice the resistance of resistor 2. The two are connected in series and a potential difference is maintained across the combination. Then the potential difference across 1 is_______ that across 2
twice
If both the plate area and the plate separation of a parallel-plate capacitor are doubled, the capacitance is:
unchanged
A battery is connected across a series combination of two identical resistors. If the potential difference across the terminals is V and the current in the battery is i, then the potential difference across each resistor is ____ and the current in each resistor is ___.
V/2, I
“The sum of the emf’s and potential differences around a closed loop equals zero” is a consequence of:
Conservation of energy
An electron is accelerated from rest through a potential difference V. Its final speed is proportional to:
Sqrt V
For loop of a current-carrying wire in a uniform magnetic field the potential energy is a minimum if the magnetic dipole moment of the loop is:
in the same direction as the field
In a three-phase synchronous converter, the ratio of the AC voltage to DC Voltage is.
0.612
True or False
A magnetic field CANNOT change the kinetic energy of a charged particle
True
For three-phase induction motors which of the following is the least efficient method of speed control?
Rheostatic control
A complex voltage wave is applied across a pure capacitor. As compared to the fundamental voltage, the reactance offered by the capacitor to the third harmonic voltage would be
One-third
Which of the following harmonic voltage components in a 3-phase system would be in phase with each other?
2nd, 4th, 6th, etc
The skin effect of a conductor will reduce as the Resistivity of conductor material ________
increases
To make a galvanometer into an ammeter, connect:
a low resistance in parallel
By which of the following methods the protection against direct lightning strokes and high voltage sweep waves is provided?
Lightning arresters and ground wires
A periodic waveform possessing half-wave symmetry has no
Even harmonics
Poles which carry transformers are usually
H-type
In a Fourier series expansion of a periodic function, the coefficient a₀ represents its
DC value
The dc motor terminal voltage supplied by a solid-state chopper for speed control purposes varies ____ with the duty ratio of the chopper
linearly
The impedance of an RLC series circuit is definitely increased if:
R increases
If the field circuit of a loaded shunt motor is suddenly opened
circuit breaker or fuse will open the circuit before too much damage is done to the motor
In a dc generator, the effect of armature reaction on the main pole flux is to:
Both reduce it and distort it
The primary reason why open-circuit test is performed on the low-voltage winding of the transformer is that it
draws sufficiently large on-load current for convenient reading
Displacement current exists wherever there is:
a changing electric field
The purpose of Milliken’s oil drop experiment was to determine:
the charge of an electron
A uniformly loaded dc distributor is fed at both ends with equal voltages. As compared to a similar distributor fed at one end only, the drop at middle point is ________.
one-fourth
Which class of induction motor will be well suited for large refrigerators?
Class C
What is the main reason that alternating current replaced direct current for general use?
AC voltage may be conveniently transformed.
According to Gauss’ law for magnetism, magnetic field lines:
form closed loops
A magnetic field exist between the plates of a capacitor while:
the capacitor is being charged
Transformer cores are laminated in order to:
minimize eddy current loss
If residual magnetism of a shunt generator is destroyed accidentally, it may be restored by connecting its shunt field
to a dc source
A positively charged ion, due to a cosmic ray, is headed through Earth’s atmosphere toward the center of Earth. Due to Earth’s magnetic field, the ion will be deflected:
east
Gauss’ law for magnetism tells us that magnetic monopoles ____________
do not exist
A solid-state chopper converts a fixed-voltage dc supply into a
variable-voltage dc supply
In a sinusoidally driven series RLC circuit the current lags the applied emf. The rate at which energy is dissipated in the resistor can be increased by:
decreasing the capacitance and making no other changes
Turn-off time of an SCR is measured from the instant
anode current becomes zero
The capacitor used in auto transformer circuit for sodium vapor lamps, is for
for improving the power factor of the circuit
The magnetic properties of material stem chiefly from:
electron magnetic dipole moments
If a shunt motor running with a load has its shunt field opened, how would this affect the speed of the motor?
It will speed up.
The di/dt capability of a thyristor increases when the gate current:
increases
On an analog wattmeter, what part of the scale is most accurate and how much does that accuracy extend to the rest of the reading scale?
The accuracy is only at full scale, and that absolute number reading is carried through to the rest of the range. The upper 1/3 of the meter is the only truly calibrated part.
A cylindrical region contains a uniform electric field that is parallel to the axis and is changing with time. If r is the distance from the cylinder axis the magnitude of the magnetic field outside the region is:
proportional to 1/r
In a mercury vapor lamp light red objects appear black due to
absence of red light from lamp radiation
A sinusoidal emf is connected to a parallel plate capacitor. The magnetic field between the plates has _______ waveform and its amplitude _______ is to the frequency of the source
sinusoidal, proportional
In an RLC series circuit, the source voltage is leading the current at a given frequency f. If f is lowered slightly, then the circuit impedance will:
decrease
The polarity of an unmarked magnet can be determined using:
a compass
In a commutation circuit, employed to turn-off an SCR, satisfactory turn-of is obtained when
Circuit turn-off time > device turn-off time
Two wires made of the same material have the same lengths but different diameters. They are connected in parallel to a battery. The quantity that is NOT the same for the wires is:
the current
When a lead-acid storage battery is being charged, a harmful effect to humans is:
Emission of hydrogen gas.
For current to flow in an NPN silicon transistor’s emitter-collector junction, the base must be:
At least 0.7 volts positive with respect to the emitter.
What occurs if the load is removed from an operating series DC motor?
It will accelerate until it falls apart.
The primary of an ideal transformer has 100 turns and the secondary has 600 turns. Then the primary current is ____ times the secondary current
six
For a Y – Δ transformer Y – side grounded, the zero sequence current exists in the
lines on they – side
In a DC motor, what is the definition of “field resistance”?
It is the resistance of the excitation circuit.
Helmholtz coils are commonly used in the laboratory because the magnetic field between them:
is nearly uniform
The disadvantages of transmission line as compared to cable system are
atmospheric hazards like smoke, ice fumes, exposures to lighting, interference of telecommunication circuits etc.
The material used for fuse wire must have
low melting point and high specific resistance
The positive sequence component of voltage at the point of fault is zero when it is a
three-phase fault
A dielectric slab is slowly inserted between the plates of a parallel plate capacitor, while the potential difference between the plates is held constant by a battery. As it is being inserted the capacitance and the charge on the positive plate _________ but the potential difference between the plates ______________
increase, remains the same
If the torque angle is continuously increasing, the system will become __________.
unstable
The effective resistance of conductor is increased by ________.
Both skin effect and proximity effect
Wideband FM is preferable to narrowband FM for music transmission because:
The fidelity is better
What characteristic of plates of the battery is where Ampere-hour is rated?
area
Receptacle outlet shall be located on or above, but not more than ______ above countertop or work surface.
500 mm
What is the maximum number of conductors in a raceway that does not need to be derated?
3
This is the maximum continuous anode direct current that the device can withstand in the conduction state under specified conditions.
average forward current
Ideal transformer assumptions do not include zero reactance of the winding. True or False?
True
“In any linear bilateral network, if a source of emf E is any branch produces a current I in any other branch, the same emf acting in second branch would produce the same current I in the first branch”. This statement is associated with ___.
Reciprocity Theorem
For small values of drain-to-source voltage, JFET behaves like a
resistor
In EPIRA, what does OARC stand for?
Open Access and Retail Competition
Name the effect which is resulted because of the size of conductor, frequency, and the specific resistance of conducting material.
proximity effect
In turning off an SCR, a particular method is used wherein this basically requires momentarily forcing current through the SCR in the direction opposite to the forward conduction so that the net forward current is reduced below the holding value. What is this method?
forced commutation
Motors must be labeled with the following nameplate rating, manufacturer’s name and etc. This is known as the _________.
manufacturing rule
What is the heating process that makes use of the currents induced by the electromagnetic action in the charge to be heated. It is used for hardening of steel?
Induction heating
What is the maximum allowable continuous load for branch circuit conductor?
0.8
The skin effect in conductors is due to non-distribution of current in it and major portion of the current is near the ________ of conductor.
surface
This is the least prevalent shunt fault among transmission and distribution lines.
LLL
A resistance having a rating of 10 ohms, 10W is like to be a ___.
Wire Wound Resistor
For proper parallel operation, ac polyphaser alternators must have the same______.
voltage rating
In a BJT, largest current flow occurs in the _____
emitter
When a power plant is not able to meet the demand of consumers it will resort to _______.
load shedding
In a capacitor the electric charge is stored in:
dielectric
A capacitance C is charged through R. The time constant of the charging circuit is given by:
RC
In steam power plant which component needs maximum maintenance attention?
Boiler
The current flowing in L and C at parallel resonant are:
equal
Overvoltage relay device function number is ______________.
59
An AM transmitter using a class-C PA should employ:
High-level modulation
The minimum size of conductors to be used for lighting purposes is _____.
2.0 mm²
At a DC steady state, capacitor looks like a/an _______ circuit and an inductor looks like a/an ______ circuit.
opened, shorted
A substance or material having relative permeability of less than unity is classified as:
Diamagnetic
The useful life of diesel engine in a power plant is expected to be ______ year/s.
15
In a junction transistor, the collector cut-off current ICBO reduces considerable by doping the collector with ________
low level of impurity
Is the Collecting Efficiency included in the evaluation of the Technical Performance of a Distribution System according to Philippine Distribution Code (PDC)?
No
In positive voltage sequence, the line voltage leads the phase voltage by 30°. True or False
True
The direction of induced EMF can be found by using the principle of ______.
Fleming`s Right Hand Rule
In the solution of load flow equation, Newton-Raphson (NR) method is superior to the Gauss-Seidel (GS) method, because the _______ of the NR methods are not affected by ___________
convergence characteristic , selection of slack bus.
In a Zener diode shunt voltage regulator, the diode regulates so long as it is kept in _______ condition.
reverse
AC system has the following disadvantages over DC system EXCEPT:
charging current exists
An emf induced by the changing of current in the neighboring coil is called:
Mutually Induced
An inductance L and resistance R are connected in series to an ideal battery. A switch in the circuit is closed at time 0, at which time the current is zero. The energy stored in the inductor is a maximum:
a long time after the switch is closed
In the analysis of short transmission lines which of the following is neglected?
Shunt admittance
Maxwell’s L/C bridge is so called because:
For balance, it uses two opposite impedances in opposite arms
The meter that is suitable for only direct current measurements is:
Permanent-magnet type
The voltage regulation in magnetic amplifier type voltage regulator is affected by:
varying the reactance
The bundling of conductors is done primarily to:
reduce reactance
The Fourier series of a waveform possessing odd quarter-wave symmetry contains only
Odd sine terms
increased effective resistance but reduced effective internal reactance of. the conductor results to
Skin effect
During storm the live conductor of public electric supply breaks down and touches the earth. The consequences will be:
current will flow to earth
DMC was created by the Energy Regulatory Commission to monitor the compliance of the distribution utilities to the PDC. DMC stands for ________.
Distribution Management Committee
In practice, the three phase conductors of a three-phase line are seldom equilaterally spaced. The usual nonsymmetrical spacing produces unequal inductances in the three phases, leading to unequal voltage drops and imbalance in the line. To offset this imbalance, the positions of the conductors are interchanged at regular intervals in the line. This practice is known as ______.
Transposition
For two alternators operating in parallel, if the load shared by one of the alternators is to be increased, the field excitation is ______ but input torque should be ________
be kept constant, increased
What characteristic of plates of the battery is where Ampere-hour is rated?
Area
The current flowing in L and C at parallel resonant are:
equal
Positive charge is distributed uniformly throughout a non-conducting sphere. The highest electric potential occurs ______.
at the center
A ________ substance is one through which the magnetic lines of force can pass very easily
permeable
In a SCR circuit, the angle of conduction can be changed by changing:
Gate current
In a capacitor the electric charge is stored in:
dielectric
It is the steady current that produces the same rate of heating in a resistor as the actual current.
rms value of an AC current
_________ are used to control both magnitude and phase of the ac line current from the utility.
Static VAR compensators
What is the primary function of the tubes welded on the side of oil-type transformer?
To improve the cooling.
In a communication system, noise is most likely to affect the signal in the ________
channel
True or False: Windows 98 is RTOS (Real Time Operating System)
False
A car battery is rated at 80 ampere-hour. An ampere-hour is a unit of _____.
charge
What does IEMOP stand for?
Independent Electricity Market Operator of the Philippines
The purpose of a grid system is to:
interconnect the power stations
It is recommended to use UJT oscillator for gate-triggering of the thyristors mainly because:
It provides sharp firing pulses.
Power factor of synchronous motor can be made leading by adjusting its:
Excitation
What does PEMC in EPIRA stand for?
Philippine Electricity Market Corporation
One primary and one secondary terminal of a two-winding transformer is connected to an ohm-meter instrument. What will be the reading on this instrument?
Infinity
True or False:
Faraday’s Law states that an induced electromotive force is proportional to the rate of change of magnetic flux.
True
Which of the following statement is CORRECT concerning electric field?
A charged point particle released from the rest moves along a field line.
The breakdown mechanism in a lightly doped p-n junction under reverse biased condition is called:
Avalanche breakdown
Does the Differential relay protective relay/s operates on the principle of the Kirchhoff’s Current Law?
Yes
In a low-level AM system, amplifiers following the modulated stage must be:
Linear devices
In a DC transmission line, are there effects due to inductive and capacitive reactances?
None
For a JFET, when V_DS is increased beyond the pinch off voltage, the drain current:
Remains constant.
Removing bypass capacitor across the emitter-leg resistor in a CE amplifier causes ______ in voltage gain
Decrease
The boundary of the protection system is determined by the location of ____________.
current transformers
Which of the following is the electrical device that is usually required to be installed in moisture area in the dwelling unit in order to protect the person from electric shock?
Ground-Fault Circuit Interrupter
String efficiency is used for measuring the:
Degree of utilization SCRs.
Guy wire is used in the construction of distribution lines for what purpose?
Supporting the pole
Which of the following refers to the power loss due to alternating magnetization and demagnetization of the core material?
Hysteresis loss
The direction of induced EMF can be found by ______.
Fleming`s Right Hand Rule
GMC was created by the Energy Regulatory Commission to monitor the compliance of the users of the Grid to the PGC. What does GMC stand for?
Grid Management Committee
The value of the resistor creating thermal noise is doubled. The noise power generated is therefore:
Unchanged
Name the effect which is resulted because of the size of conductor, frequency, and the specific resistance of conducting material.
proximity effect
When transistors are used in series or parallel, a snubber circuit is used to:
Limit di/dt
When the amplitude of the oscillator in a series RLC circuit is doubled, the Current amplitude is ___________.
doubled
The skin effect in conductors is due to non-distribution of current in it and major portion of the current is near the ________ of conductor.
surface
A capacitance C is charged through R. The time constant of the charging circuit is given by:
RC
The effective resistance of conductor is increased by ________.
Both skin effect and proximity effect
True or False
A pre-emphasis circuit provides extra noise immunity by amplifying the high audio frequencies
True
If both the resistance and the inductance in an LR series circuit are doubled the new inductive time constant will be:
unchanged
True or False:
Capacitor motors have lower starting torque than comparably sized single-phase induction motor.
False
The ________ is used to protect the Oil immersed transformers against all internal faults
Buchholz relay
According to Gauss’ law for magnetism, magnetic field lines forms:
closed loops
Three phase transformers which cannot be connected in parallel are
Y – Y with Y – Δ
True or False: Magnetic flux lines do not have sources or sinks.
True
True or False:
A compound motor’s speed remains fairly constant when subjected to sudden loads
False
Lightning arresters are located _______
Near the transformer
Corona loss can be reduced by the use of hollow conductor because:
for a given cross-section, the radius of the conductor is increased
For the stable operation of interconnected system, the passive element that can be used as interconnecting element is:
reactor
In which of the following given faults, all the sequence currents are equal?
LG
If the transmission voltage increased, the percentage resistance drop will:
Decrease
The magnetic saturation curve limits the voltage at which a generator or motor can operate. Does saturation depend upon the type of steel used in the poles.
No
A battery is used to charge a parallel-plate capacitor, after which it is disconnected. Then the plates are pulled apart to twice their original separation. This process will double the:
stored energy
A DC system can be protected from lightning by including a thyrite tube in the circuit that connects the high-voltage line with the ground. Does its fusable link melt at high voltages?
No
Two parallel-plate capacitors with the same plate separation but different capacitances are connected in parallel to a battery. Both capacitors are filled with air. The quantity that is NOT the same for both capacitors when they are fully charged is:
charge on the positive plate
Do magnetic field lines cross themselves only at right angles?
No.
In a DC motor, what is the definition of “field resistance”?
It is the resistance of the excitation circuit.
Which of the following effects are generally less for an alternating current than for a direct current?
Chemical effects
The material used for fuse wire must have:
low melting point and high specific resistance
The class C insulation can withstand:
180°C
The percent bias for a generator protection lies between ____ to ____.
5 to 10
An essential requirement of peak load plant is that It should be capable of ________
starting quickly.
Induction regulators are used for voltage control in what part of the power system?
primary distribution
True or False
The current is produced by both holes and electrons when a P-N junction is forward-biased:
True
Floating neutral, in 3-phase supply, is undesirable because it causes:
unequal line voltages across the load
Which should be used for extinguishing electrical fires?
Carbon tetrachloride fire extinguisher
The ripple factor of a power supply is a measure of:
its filter efficiency
Power loss due to corona is not directly proportional to spacing between conductors. True or False
True
As compared to a LED display, the distinct advantage of an LCD display is that it requires ________ power
extremely low
The leakage current of a P-N diode is caused by:
heat energy
The magnetic saturation curve limits the voltage at which a generator or motor can operate. Does saturation depend upon the type of steel used in the poles?
No
For a lumped inductive load, with increase in supply frequency, P _______ and Q ________
decreases, increases
FDLF method is suitable for
high voltage transmission system
Which material is used for the manufacture of bus bars?
Copper rods
Why solid type of conductors is not preferred for the voltages exceeding 66 kV?
A danger of breakdown of insulation.
If any two phases for an induction motor are interchanged:
The motor will run in the reverse direction.
Are contact devices used for the measurement of level more reliable than devices which do not make contact with the material?
No
The term ‘cogging’ is associated with:
Induction motor
The good power factor of an induction motor can be achieved if the average flux density in the air gap is ____.
small
The thickness of insulation provided on the conductor in the cable depends on which among the following factors?
Operating voltage
The stator core is usually fabricated out of _______
Silicon steel
What kind of reactor is used to bring down the fault level within the capacity of the switchgear instrument?
Series reactor
In the manufacture of transformers, ANSI prescribes certain standards. One of it is that high voltage side should lead the low voltage side by 30° with Y - Δ or Y - Δ connections. True or False
True
Why is the single core cable not provided with armoring?
Avoids excessive loss in the armor.
In this gauge, the Low pressure fluid is compressed to a high pressure which is read by the monometer technique.
McLeod gauge
What is the value of the zero-sequence current compared to the current in the neutral wire?
1/3 times
Bedding’s purpose is both to protect the sheath against corrosion and to protect the sheath from mechanical injury due to armoring. True or False
True
In fiber-optic level sensors, the amount of light loss depends on:
The proportion of cable that is submerged in the liquid.
For induction motor at standstill condition, what is the value of slip?
1
In three-phase squirrel-cage induction motors, rotor conductors are short-circuited through end rings. True or False?
True
Can the rotameter be used for the application in automatic control scheme?
Yes
If real power demand is suddenly increased, frequency of the system will ______.
decrease
A squirrel-cage motor has such low resistance that it draws excessive current when starting. Will using a class A motor reduce this problem?
No
The rapid exponential decay in just a few cycles of the charge on the plates of capacitor in an RLC circuit might be due to:
a large resistance
Voltage magnitude of a particular bus can be controlled by controlling the:
reactive power of the bus
In terms of efficiency, shunt and series motors or generators have similar characteristics. Does the two type of motor have very similar efficiency curves?
No
Series and shunt motors are connected like series and shunt generators, respectively. The terms refer to the manner in which the self-excitation of the poles is connected to the unit.
Is it true that the torque curves of both shunt and series motors are not affected by the value of the armature current.
False
A long transmission line has certain values of parameters A, B, C, D. If the length is made 100 km thus the parameter A ________ and B _______
A increases B decreases
What will be the electrostatic force between the bodies, if the magnitude of the charge on two identical charged bodies is doubled?
Quadrupled
Two charges Q₁ and Q₂ are separated by a distance D. what is the effect on the force if Q₁, Q₂ and D are all doubled?
Remains the same
Friction and windage losses in induction motor is _______ of rated output.
1%
It is the decrease in dielectric strength of any mixtures of gases.
Penning effect
In lap winding, equalizer rings are used to save:
Brushes from carrying circulating currents.
Current chopping mainly occurs in which circuit breaker?
Air plant circuit breaker
The frequency of the humming tone in a transformer is _____
100 Hz.
For Paschen’s law to be valid which is the essential condition?
Temperature must be constant
Which part of the transformer is most prone to damage due to overheating?
Winding insulation
Fuse wire protection system is not used beyond:
100 A
Consider two capacitors. The second of two capacitors has twice the charge and half the voltage. What is the capacitance of the second capacitor?
Four times that of the first
When all the 3 phases are short circuited, it gives rise to:
Symmetrical fault current
For a simple lap winding, the commutator pitch is equal to:
± 1
The percentage of silicon in transformer stamping is usually limited to ____.
4%
The shaft of electric motor is generally supported in:
Ball or roller bearing
At what power angle the transmission line should be operated for stability and economy?
30° to 45°
The main consideration for higher operating voltage of transmission is to:
increase power transfer capability
The effects of electric shock in the human body will depend on:
current flowing in the body
What do you call the peripheral distance between the center of two adjacent poles in a DC machine
Pole pitch
Regarding rotating machinery, at zero power factor, the generator delivers real power to a load. True or False?
False
The area of hysteresis loop is a measure of:
Energy loss per cycle
Coulombs law for the force between electric charges most closely resembles with:
Newton`s law of gravitation
When two electricity neutral materials are rubbed together, one acquires a net positive charge and the other:
Gains electrons
________ is the amount of energy which must be given to an electron to move it to valence band
Fermi energy
What is the resistivity of semiconductor at room temperature?
0.01 to 50 ohm–cm
Is Electric Field Intensity a vector quantity?
Yes
What do you use to measure the dissipating factor of a capacitor?
Schering Bridge
Two charges Q1 and Q2 are separated by a distance D. what is the effect on the force if Q1, Q2 and D are all doubled?
Remains the same
The number of atoms or ions surrounding and touching a central atom is called
Ligancy
What will be the electrostatic force between the bodies, if the magnitude of the charge on two identical charged bodies is doubled?
Quadrupled
Which law is the magnetic equivalent of coulomb’s law?
Biot savart law
Temperature beyond which substances lose their ferroelectric properties is known as:
Curie temperature
The line imperfection in a crystal known as ______.
Edge dislocation
What is the value of dielectric constant for most of the solid substance?
Between 1 and 10
According to Steinmetz Hysteresis Law, hysteresis loss in a material is proportional to the flux density raised to:
1.6
Can Teflon be used at temperatures above 100 degrees C?
Yes
What is the percentage of carbon in mild steel?
0.08 to 0.3%
Is Pelton wheel a reaction turbine?
No
Measurement of ________ is affected by the presence of thermo-emf in the measuring circuit
high resistance
High voltage transmission efficiency is in the range of
85-95%
A BJT is said to be operating in the saturation region if
both the junctions are forward biased
In suspension type insulator the potential drop is maximum across the _____
lowest disc
In which industry are all the motors totally enclosed and moisture proof?
Paper industry
In a 3-phase synchronous generator, the stator winding is connected in star, because a delta connection would
have circulating currents due to triple harmonics
EMF induced in a coil rotating in a uniform magnetic field will be maximum when the rate of change of flux linkage is:
maximum
The response time of an indicating instrument is determined by its
damping system
What bridge is generally used for measurement of frequency and also capacitance?
Wein bridge
If the frequency of a transmission system is changed from 50 Hz to 100 Hz, the string efficiency
will decrease
The number of commutator segments in a dc machine is equal to the number of:
Coils
A DC voltage source is connected across a series RLC circuit. Under steady state conditions the applied DC voltage drops entirely across the:
C only
The number of parallel paths in an integral slot winding with P poles is:
P/2
The voltage of the bus-bar to which several alternators that are paralleled may be raised by simultaneously increasing field excitation of all alternators. True or False
True
Oil for transformer cooling should have ____ viscosity
Low
Why is skewing done in rotor slots?
To suppress unwanted harmonics.
What type of winding is the armature of a dc machine?
A closed-circuit winding.
When two electricity neutral materials are rubbed together, one acquires a net positive charge and the other
Gains electrons
When will the amount of back emf of a shunt motor increase?
When the field is strengthened.
Resistance switching is normally employed in what circuit breakers?
air blast circuit breakers
Which material for heating element should be selected if a furnace is to be used for heating up to temperature around 1500°C?
Platinum-molybdenum carbon compound
Low frequency operation of AC series motor in traction application Improves its:
commutation, pf and efficiency
The damping in D’ Arsonval galvanometer is obtained by ______.
eddy current induced in metal discs
The purpose of choke in a fluorescent tube is to _____.
increase voltage momentarily
Consider a constant uniform magnetic field. A conductor moves across this field at a constant velocity. The emf induced in the conductor is termed as ____.
dynamically induced emf
What is the pitch factor for a full pitched winding of a synchronous machine?
1.0
In which single-phase motor, the rotor has no teeth or winding?
Hysteresis motor
In the measurement of power in a balanced 3 phase circuit by two-wattmeter method if the two wattmeter’s show equal readings, then what is the power factor of the circuit?
unity
Alternator used in hydropower station has more number of poles in it than used in thermal power station, because
speed of its prime mover is less
The household energy meter is what kind of instrument?
integrating instrument
A commutator in a dc machine provides __________ rectification.
Full wave
What is the range of thickness of lamination of the core of a power transformer?
0.03 to 0.5 mm
When back emf of a dc motor vanishes suddenly, then:
The motor burns.
In class – B dc motor, what is the maximum permissible temperature rise in the armature winding?
75 degrees C
For induction motor, the ratio of length to pole pitch for good efficiency is taken as:
1.5 to 2
Can Mica be used for temperatures up to 500 degC?
Yes
The unvarying load on a power station which occurs almost the whole day on the station is known as:
Base load
Does the frequency contribute to the dielectric loss due to conductivity?
No
At Neel temperature Susceptibility is:
maximum
With respect to dc motors, what do you call the losses in armature and series field winding
direct load loss
Materials which lack permanent dipoles are called:
Diamagnetic
What is the approximate percentage of volatile matter in coal?
25 – 35 %
In a permanent magnet dc motor, can the method of varying the field current be used to control its speed?
No
Potential transformers are used to measure
high a.c. voltage
Two D.C. series motors are connected in series to produce a torque T. Now if the motors are connected in parallel, what will be the torque produced?
T/4
For arc heating, the electrodes are made of _____.
graphite
A PN junction is _______.
a rectifier
Zero power factor method for an alternator is generally used to determine
voltage regulation of alternator
Which electric discharge lamps gives highest lumens per watt?
Sodium vapor lamp
How many different speeds can be obtained in cascade control of two induction motors?
4
A three-phase power transformer is provided with star-delta connections. In order to protect against fault, connection for current transformer should be in _______.
delta-star
For active region operation of NPN transistor, emitter is _____ with respect to base
negative
A series resonant circuit implies unity power factor and ______ current
unity, maximum
Mho relay is used to protect _____ transmission lines
long
If supply frequency increases, the skin effect
increases
What is the percentage slip in case of synchronous motor?
zero
If a combination of HRC fuse and circuit breaker is used, the circuit breaker operates
under all abnormal currents
What is the practical permissible variation of frequency in power system?
± 3%
Distribution transformers are designed to have maximum efficiency nearly at
50% of full load
True or False: 1 Ampere-turn = 4π Gilberts
False
In a transmission line, if the load is suddenly increased in the receiving end of the system, the phase shift will:
Increase
In approximately how many cycles can a high-speed circuit breaker complete its operation?
3 to 8
Energy formation of Schottky defect in a metal is of the order of ______.
1 eV
For an alternator operating at no load before the fault occurs, voltage of the alternator |Eg| divided by the steady state current |I| (rms value) is known as:
(d – axis) synchronous reactance Xd
Why are direct-on-line starters not suitable for starting large dc motors?
Large voltage drop may occur
What will be the effect of a crock in the magnetic path of inductor?
Reduced inductance
What is the cause of output voltage produced across the crystal in Hall’s effect?
Movement of charge carriers towards one end
Why is the compensating winding provided in a dc motor?
To prevent commutator flash over
The change in dimensions during the process of magnetization is called ______.
magnetostriction
What is the rated voltage of low voltage circuit breakers?
Less than 1000 V
In balanced 3ϕ system, negative and zero phase sequence currents are:
Zero
It is the process of demagnetizing metallic parts.
Degaussing
What is the most common type of fault on the overhead transmission line?
Single line to ground fault
Teflon is prepared by catalytic polymerization of _______.
tetrafluroethline
In a house lighting circuit, if a 5A fuse blows frequently, it is required to:
Check the load
On tripling the number of turns of a coil, the inductance becomes
_______.
9 times as large
When a magnet is in motion relative to a coil the induced emf does not depend upon:
Resistance of the coil
In practice, earth is chosen as a place of zero electric potential because it
has almost constant potential
A steel mill requires a motor having high starting torque, wide speed range and precise speed control. Which type of motors will you choose?
DC series motors
The positive and negative halves of a complex wave are symmetrical when:
It contains odd harmonics
The most useful ac bridge for comparing capacitances of two air capacitors is ________ bridge.
De Sauty
The frequency corresponding to half-power point on the response curve of a filter is known as _________.
cutoff
Any charge given to the battery when taken off the vehicle is called _____ charge.
bench
A periodic function has zero average value over a cycle and its Fourier series consists of only odd cosine terms. What is the symmetry possessed by this function?
Even quarter-wave
Double-energy transients are produced in circuits consisting of
resistance, inductance and capacitance
The rms value of sinusoidal ac current is equal to its value at an angle of ____ degree.
45
A complex voltage wave is applied across a pure capacitor. As compared to the fundamental voltage, the reactance offered by the capacitor to the third harmonic voltage would be ______.
one-third
Single-phase synchronous motors are used in teleprinters, clocks and all kinds of timing devices because of their ______.
constant speed
The motor used for intermittent light torque load is:
Commutative compound motor
A keeper is used to:
Provide a closed path for flux
The magnetic moment developed per unit volume of the substance is known as:
Intensity of magnetization
For a simple lap winding, the winding pitch is equal to:
± 2
Under commutation gives rise to:
Sparking at the tailing edge of the brush
The coefficient of coupling between two air core coils depends on:
Mutual inductance and self-inductance of the two coils
The electric power being transmitted from generating point is called:
Primary transmission
The span of transmission like between towers takes the shape of:
Parabola
For a lap winding, how are the no. of poles and no. of parallel paths (A) are related?
P = A
According to which law when conductor cuts magnetic flux an emf is induced in the conductor?
Faraday`s law
Wooden poles can be used for a span of maximum up to:
160 m
Which insulator can be used to change the direction of transmission line?
Strain type
The efficiency of dc machine is maximum when variable loses are equal to:
Constant losses
Which gas is sometimes used in filament lamps?
Argon
An auto transformer used with sodium vapor lamp should have _____ leakage reactance
high
In lap winding number of brushes is Equal to
number of poles
In an R-L series circuit, the phase difference between applied voltage and circuit current will increase if X_L is:
increased
In a fluorescent tube circuit, the function of choke is primarily to
initiate the discharge
When the amplitude of the oscillator in a series RLC circuit is doubled the current amplitude is:
doubled
The function of interpoles in a DC machine is to improve ______.
commutation
For alternators working in parallel, the machines must have equal kVA ratings. True or False
False
What type of protection does not respond to faults occurring beyond its zone even though the fault current may happen through the zone?
Unit protection
The current drawn by a tungsten filament lamp is measured by an ammeter. The ammeter reading under steady state condition will be ________ the ammeter reading when the supply is switched on.
less than
Superposition theorem can be applied only to ______ networks.
linear and bilateral
For V-curves for a synchronous motor the graph is drawn between:
field current and armature current
In RLC circuit, the current at resonance is ______ in series circuit and _____ in parallel circuits
Maximum, minimum
According to which theorem, the number of voltage (or current source) can be combined directly into a single voltage (or current source)?
Millman`s theorem
What is the ambient temperature for design of transformer?
45°C
If the internal resistance of voltage source is zero, the voltage across the source is equal to the terminal voltage (across the load) and is independent of the amount of load current. Such a voltage source is called:
Ideal voltage source
True or False:
For a voltage source, terminal voltage cannot be higher than source voltage
True
If a capacitor is charged by a square wave current source, the voltage across the capacitor is ________ wave
Triangular
What is the condition of current and pf in series LCR circuit at resonance?
Current is maximum pf is unity
A network is said to be nonlinear when it does not satisfy ___________.
superposition condition
A series resonant circuit is capacitive at f = 100Hz. The circuit will be inductive somewhere at f ______ 100 Hz.
less than
What should be the position of the terminals across the voltage source to neglect the voltage source?
Short circuited
Changes in stored energy in inductors and capacitor causes the flow of transient current in a circuit. True or False?
True
What will be the effect on angle between voltage and current, if a small capacitance is added in series to a lightly inductive circuit?
It decreases.
The part of a network to which two or more circuit elements are connected is called:
Node
A circuit having identical properties in either direction is known as:
Bilateral circuit
The phenomenon of corona reduces the losses of the line. True or False?
False
Under __________ theorem to find the equivalent impedance, all independent voltage sources are short circuited and all independent current sources are open circuited
Thevenin’s
Application of Norton’s theorem to a circuit yields equivalent ______ source and impedance in ______
current, parallel
With same maximum voltage between conductors, the ratio of copper volumes in 3-phase, 3-wire system and 1-phase, 2-wire system is
3/4
The purpose of the conservator in a transformer is
to prevent moisture in the transformer
For ac transmission lines less than 80 km in length, it is usual to lump the line capacitance at
the receiving end
Which of the AC bridges is preferred for the measurement of inductance having high Q-factor?
Hays bridge
Area of hysteresis loop represents ________ loss.
hysteresis
The capacitance of a parallel-plate capacitor can be increased by the _______ plate separation
decreasing
The current density is the same in two wires. Wire A has twice the free-electron concentration of wire B. The drift speed of electrons in A is:
half that of electrons in B
Two alternators A and B are sharing the inductive load equally. When the excitation of A is increased, current delivered by A will _____ and B will ______
increase, decrease
The torque exerted by an electric field on a dipole is ________ to both the field and dipole moment
perpendicular
For an ohmic substance the resistivity is the proportionality constant for:
current density and electric field
Which of the motors is preferred when quick speed reversal is the main consideration?
Synchronous motor
The ordinary efficiency of a given transformer is maximum when its Cu loss _______ iron loss
equals
In a dc motor, the mechanical output power actually comes from _____.
electrical input power
In a transformer, the leakage flux of each winding is proportional to the current in that winding because the _____do not saturate.
leakage paths
Which dc motor would be suitable for drivers requiring high starting torque but only fairly constant speed such as crushers?
Compound
The primary function of a clamper circuit is to:
introduce a dc level into an ac signal
If the height of transmission tower is increased The line capacitance will _________ but line inductance will _________.
decrease, remain uncharged
As compared to shunt and compound motors, a series motor has the highest torque because of its comparatively ________ at the start.
stronger series field
The main disadvantage of Hopkinson’s test for finding efficiency of shunt dc motors is that it:
requires two identical shunt machines
Large capacity generators are invariably:
hydrogen cooled
For a consumer, the most economical power factor is generally:
0.95 lagging
The chief advantage of Ward-Leonard system of dc motor speed control is that is _______.
gives smooth, sensitive and wide speed control
Corona usually occurs when the electrostatic stress in air around the conductor exceeds:
30 kV (maximum value)/cm
Recombination takes place when:
an electron falls into a hole
In practice, regenerative braking is used when:
load has overhauling characteristics
A synchronous condenser is virtually an Overexcited synchronous motor. True or False?
True
If an intrinsic semiconductor is doped with a very small amount of boron, then in the extrinsic semiconductor so formed, the number of electrons and holes will ______.
decrease and increase respectively
When a live conductor of public electric supply breaks down and touches the earth what will happen?
Current will flow to earth
The magnitude of the Bohr magneton in J/T is about:
10¯²³
The most efficient form of damping employed in electrical instruments is:
Eddy currents
If field resistance of a dc shunt generator is increased beyond its critical value, the generator:
will not build up
During the charging of a lead-acid cell its voltage ________.
increases
Why is the outer surface of the cardboard center of a paper towel roll cannot be a Gaussian surface ?
because it is not a closed surface
As compared to constant-current system, the constant-voltage system of charging a lead-acid cell has the advantage of:
Both Reducing time of charging and Increasing cell capacity
A hollow conductor is positively charged. A small uncharged metal ball is lowered by a silk thread through a small opening in the top of the conductor and allowed to touch surface. After the ball is removed, it will have ______ charge
no appreciable
The unit of absolute permittivity of a medium is:
Farad/meter
The maximum torque by dc motors is limited by:
commutation
The magnetic dipole moment of an atomic electron is typically:
a few Bohr magnetons
If load on a dc shunt motor is increased, its speed is decreased due primarily to ________ in back emf
decrease
The intrinsic magnetic dipole moments of protons and neutrons are much less than that of an electron because:
their masses are greater
_______ bridge is used for measuring an unknown inductance in terms of a known capacitance and resistance.
Anderson
As the load is increased, the speed of a dc shunt motor:
reduces slightly
In a simple high-pass RC filter, if the value of capacitance is doubled, the cutoff frequency is:
halved
The molecular theory of magnetism can explain why an N pole attracts a S pole. True or False?
False
A bar magnet is broken in half. Each half is broken in half again, etc. The observation is that each piece has both a north and south pole. Thus, usually explained by __________ that all magnetic phenomena result from electric currents
Ampere`s theory
Ward-Leonard system of speed control is not recommended for:
constant speed operation
The all-day efficiency of a transformer depends primarily on:
both the amount of load and the duration of load
The energy of a magnetic dipole in an external magnetic field is least when the dipole moment is ________ to the field
parallel
Magnetization vectors in neighboring ferromagnetic domains are always in _________ directions
different
The behavior of ferromagnetic domains in an applied magnetic field gives rise to:
hysteresis
The electric field in unpolarized light:
changes direction randomly and often
Transmission voltage of 11 kV is normally used for distance up to
20 to 25 km
In dc generators, armature reaction is produced actually by ______.
load current in armature
Series capacitors on transmission lines are of little use when the load VAR requirement is _____.
small
A magnetic field exerts a force on a charged particle if the particle is moving ______
across the field lines
Lap winding is suitable for ______ current, _______ voltage dc generators.
high, low
When the frequency of the oscillator in a series RLC circuit is doubled the capacitive reactance is ______
halved.
A low utilization factor for a plant indicates that plant is used for
stand by purpose only.
Electric Field lines are close together where the field is large. True or False?
True
An outstanding feature of a universal motor is its:
Highest output kW/kg ratio
What is otherwise known as “PRC Modernization Law”?
RA 8981
One of the characteristics of a single-phase motor is that it is not self-starting. True or False?
True
The synchronous speed of a linear induction motor does not depend on number of poles. True or False?
True
The rapid exponential decay in just a few cycles of the charge on the plates of capacitor in an RLC circuit might be due to:
A large resistance.
While calculating the cost of electric power generation, repair and maintenance is NOT considered a fixed cost. True or False?
True
Negative feedback reduces distortion in an amplifier only when it:
Is generated within the amplifier
For an ohmic resistor, resistance is the proportionally constant for:
Current and potential difference.
Two of Maxwell’s equations contain a path integral on the left side and an area integral on the right. For them the path must be the boundary of the area. True or False?
True
You push a permanent magnet with its north pole away from you toward a loop of conducting wire in front of you. Before the north pole enters the loop the current in the loop is:
counterclockwise
Displacement current exists in the region between the plates of a parallel plate capacitor if:
the capacitor is being discharged
Suppose you are looking into one end of a long cylindrical tube in which there is a uniform electric field, pointing away from you. If the magnitude of the field is decreasing with time the field lines of the induced magnetic field are:
circles
The statement that magnetic field lines form closed loops is a direct consequence of:
Gauss` law for magnetism
A magnetic field parallel to the x axis with a magnitude that decreases with increasing x but does not change with y and z is impossible according to:
Gauss` law for magnetism
The magnetic field of Earth is roughly the same as that of a magnetic dipole with a dipole moment of about:
10²³ J/T
Suppose you are looking into one end of a long cylindrical tube in which there is a uniform electric field, pointing away from you. If the magnitude of the field is decreasing with time the direction of the induced magnetic field is:
counterclockwise
At any instant of time the total magnetic flux through a stationary conducting loop is less in magnitude than the flux associated with an externally applied field. This might occur because the applied field is normal to the loop and increasing in magnitude. True or False?
True
The electrical analog of a spring constant k is:
1/C
A charged capacitor and an inductor are connected in series. At time = 0 the current is zero, but the capacitor is charged. If T is the period of the resulting oscillations, the next time after t = 0 that the energy stored in the electric field of the capacitor is a maximum is:
T/2
Two wires made of different materials have the same uniform current density. The carry the same current only if:
their cross-sectional areas the same
A copper hoop is held in a vertical east-west plane in a uniform magnetic field whose field lines run along the north-south direction. The largest induced emf is produced when the hoop is:
rotated about an east-west axis
A wire carrying a large current i from east to west is placed over an ordinary magnetic compass. The end of the compass needle marked “N” will point:
south
A series circuit consists of a battery with internal resistance r and an external resistor R. If these two resistances are equal (r = R) Then the thermal energy generated per unit time by the internal resistance r is:
the same as by R
The emf developed in a coil X due to the current in neighboring coil Y is proportional to the:
rate of change of magnetic field in x
The terminal potential difference of a battery is less than its emf:
only when the battery is being discharged
A square loop of wire lies in the plane of the page. A decreasing magnetic field is directed into the page. The induced current in the loop is:
clockwise
The emf that appears in Faraday’s law is around ________ used to compute the _________
the boundary of the surface, magnetic flux
If the magnetic flux through a certain region is changing with time:
an emf must exist around the boundary
The unit of magnetic dipole moment is:
ampere·meter²
If the radius of a pair of Helmholtz coils is R then the distance between the coils is:
R
A rectangular loop of wire is placed perpendicular to a uniform magnetic field and then spun around one of its sides at frequency f. The induced emf is a maximum when:
the flux is zero
For a cylindrical resistor made of ohmic material, the resistance does NOT depend on:
the current
A constant current is sent through a helical coil. The coil tends to get _______
shorter
In a conductor carrying a current we expect the electron drift speed to be _________ the average electron speed
much less than
The magnetic field B inside a long ideal solenoid is independent of the cross-sectional area of the solenoid. True or False?
True
The disadvantage of oil when used as an arc extinguishing medium in the oil circuit breaker is that during arcing, oil producers carbon particles. True or False?
True
Slip of a 3-phase induction motor may be expressed as the ratio of
rotor copper loss over rotor power input
In general, if a sine wave is fed into a Schmitt trigger, the output will be a/an ______ wave
square
The most appropriate way of mitigating the problem of interference between power line and commutation line is to:
Transpose the power line.
A coil with a certain number of turns has a specified time constant. If the number of turns is doubled, its time constant would:
become doubled
What is the slip when the rotor of a three-phase induction motor is blocked?
1
In star-delta starting of three-phase induction motor the starting voltage is reduced to:
1/sqrt 3 times of normal voltage
In phantom loading arrangement, energy consumption in the calibration test of wattmeter is reduced because of:
the absence of load in the test set
Which one of the following does not employ a null method of measurement?
Megger
A non-sinusoidal periodic waveform is free from DC component, cosine components and even harmonics. The waveform has _____ wave and ________ symmetry
half, odd function
For balanced 3-phase supply system, the phasor sum of the line currents is NOT zero if the load is:
unbalanced star connected
Under thermal equilibrium in a pure semiconductor the ratio of the number of holes to the number of conduction electrons is:
1
In a series resonance circuit, what is the impedance at half power frequencies?
(sqrt 2)(R)
The torque developed in a DC series motor in unsaturated magnetic circuit condition requires ________.
large conductor and more core material.
It is possible to increase the field flux and, the same time, increase the speed of a dc motor provided its ________ is held constant.
armature current
In the circle diagram for a 3-ϕ induction motor, the diameter of a circle is determined by:
total stator current
The only advantage of corona is that it:
Works as safety-valve for surges.
Is it true that for the parallel operation of transformers, they must have equal kVA ratings?
False
The most efficient method of increasing the speed of a 3.75 kW dc shunt motor would be the ________ method.
flux control
The external characteristic of a shunt generator can be obtained directly from its __________ characteristic.
open-circuit
The simplest way to shift load from one dc shunt generator running in parallel with another is to __________.
adjust their field rheostats
Most commercial compound dc generator are normally supplied by the manufacturers as over compound machines because Degree of compounding can be adjusted by using a divertor across series field. True or False?
True
One of the main advantages of Swinburne’s test is that it:
Is very economical and convenient
The volume of copper required for an ac transmission line is inversely proportional to:
Both voltage and power factor
The primary reason for providing compensating windings in a dc generator is to:
Neutralize cross-magnetizing flux
The most economical method of finding no-load losses of a large dc shunt motor is ____ test.
Swinburne`s
The power factor of a squirrel-cage induction motor is low at:
light loads only
It is a measure of amount of charge that moves past a point per unit time
Current
Which dc generator cannot build up on an open circuit?
series
If the impedance triangles of two transformers operating in parallel are not identical in shape and size, the transformers will:
run with different power factors
A shunt-derived series-fed feedback in an amplifier both decreases its output impedance and increases its input impedance. True or False?
True
Two parallel-plate capacitors with different capacitance but the same plate separation are connected in series to a battery. Both capacitors are filled with air. The quantity that is the same for both capacitors when they are fully charged is:
charge on the positive plate
Two identical capacitors, each with capacitance C, are connected in parallel and the combination is connected in series to a third identical capacitor. The equivalent capacitance of this arrangement is:
2C/3
One of the following given choices for polyphase transformer connections which one will you select for three-to-two phase conversion?
Scott
The magnetizing current drawn by transformers and induction motors is the cause of their ______ power factor.
lagging
A triac can be triggered into conduction by:
both positive or negative voltage at either anode and positive or negative voltage at gate
The primary and secondary windings of an ordinary 2-winding transformer always have a common:
magnetic circuit
The torque developed by a 3-phase induction motor depends on the following three factors:
Rotor emf, rotor current and rotor p.f.
The normal value of the armature resistance of a dc motor is
0.5
Retardation test on a dc shunt motor is used for finding ______ losses.
stray
The marked increase in kVA capacity produced by connecting a 2-winding transformer is increased when connected as an autotransformer because energy is transferred both inductively and conductively. True or False?
True
Which one of the following types of generators does not need equalizers for satisfactory parallel operation?
under-compound
________ is particularly useful for measuring Inductive impedance with large phase angle
Hay’s bridge
The shaft torque of a dc motor is less than its armature torque because of _______ losses.
rotational
The _______ scheme allows the disconnection of circuit breaker for maintenance without interrupting the service.
transfer bus
The electric field on equipotential surface is ________ to surface:
Parallel
What do you call the protective angle between the Overhead ground wire and the power cable in the Transmission tower?
Shielding angle
What is the voltage required in arc welding by dc supply?
50 to 60 V
For a simple lap winding, the commutator pitch is equal to:
± 1
The size of the feeder is determined primarily by:
The current it is required to carry
The conductors are bundled primarily to:
Reduce reactance
Hysteresis loss varies with flux density as:
B^1.6
The percentage of overload of a continuous rating machine is:
10 %
Which class is not one of the classes of arresters?
transmission class
Bundled conductors are used in transmission lines, the effective capacitance and inductance will respectively.
Increase and Decrease
The spacing between phase conductors of a 220 kV line is approximately equal to:
6 m
The presence of an earth in case of overhead lines:
Increases the capacitance
The fractional pitch to eliminate 7th harmonic from alternator emf is:
6/7
In neon signs, neon with a mixture of mercury gives:
Green color
Green color
Skin effect
Which component connects the substation to the area where power is to be distributed?
Feeders
A combination of switch and fuse:
safety switch
Disconnecting switch is provided for proper protection of electric substations and power plant. What is its main function?
For complete isolation
If variable part of annual cost on account of interest and depreciation on the capital outlay is equal to the annual cost of electrical energy wasted in the conductors, the total annual cost will be minimum and the corresponding size of conductor will be most economical. This statement is known as:
Kelvin`s Law
The main purpose of using core in a transformer is to decrease reluctance of the common magnetic circuit. True or False
True
For radiant heating around 2250 degrees Celsius, the heating elements are made of ____.
tungsten alloy
Which stage of a dc power supply uses a Zener as the main component?
Regulator
The usual test for determining the efficiency of a traction motor is the ______ test.
Field`s
_________ circuits are employed for lowering the level of a dc voltage.
Thyristor chopper
The emitter of a transistor is generally doped the heaviest because it has to:
dissipate maximum power
Skin effect exists only in ____ transmission.
ac
In a synchronous motor, the magnitude of stator back emf depends on
dc excitation only
The series-parallel system of speed control of series motors widely used in traction work gives a speed range of about:
1:4
The capacitor in a capacitor-start induction-run ac motor is connected in series with ______ winding.
starting
When the amplitude of the oscillator in a series RLC circuit is doubled, the current amplitude is:
doubled
An unmagnetized steel bar is placed inside a solenoid. As the current in the solenoid is slowly increased from zero to some large value, the magnetization of the bar increases with increasing current at first but later is much less affected by it. True or False?
True
Lines of the magnetic field produced by a long straight wire carrying a current forms:
circles that are concentric with the wire
A series RC circuits is connected to an emf source having angular frequency ω. The current _____ the source emf by an angle ______
leads, tan¯¹ (1/ ωCR)
Improper biasing of a transistor circuit leads to:
distortion in output signal
The starting winding of a single-phase motor is placed in the ____.
stator
The voltage regulation of an overcompound dc generator is always __________.
negative
The main function of interpoles is to minimize _________ between the brushes and the commutator when the dc machine is loaded.
sparking
The overall bandwidth of two identical voltage amplifiers connected in cascade will be _______ than that of a single stage
better
The principle of operation of a 3-phase induction motor is most similar to that of a:
Transformer with a shorted secondary
The material generally used for armor of high voltage cables is ____.
steel
Which of the polarization results from separation of positive and negative ions in molecules formed by transfer of electron from one atom to another in the molecule?
Ionic polarization
In the first column of the Routh table, if zero appears, the system is:
Unstable
Why is a starter necessary to start a dc motor?
To limit starting current to a safe value.
The amount of radiant heat produced by a fluorescent lamp is nearly what percent of that of a filament lamp of same rating?
20%
Rate of energy radiation in the form of light waves is called ______.
luminous flux
In a closed loop system, the function of the _______ is to generate the appropriate control signal applied to plant
controller
A coil of 150 degrees pitch has third harmonic pitch factor as:
cos 45°
Illumination level required for precision work is around:
500 lm/m²
Based load plants are designed to supply power at _____capital cost and ______ operating cost:
High, low
Which of the following laws states that total electric flux coming out from a closed surface is proportional to the net amount of charge enclosed by the surface?
Gauss`s law
Gilbert is the unit of:
Magnetomotive force
In a basic amplifier, in a negative feedback system with a loop gain T, the noise generated:
Decreases by a factor of (1 – T)
Under full load running condition, the slip of a synchronous motor is:
0
In gas welding, the gases used are:
Acetylene and oxygen
Capacitor A has capacitance C1 and voltage V1. Capacitor B has twice the voltage and capacitance C1. Its energy U2 equals:
2 U₁
What is the maximum permissible water content in transformer oil?
50 ppm
Rotor shaft of 500 MW alternator is supported by:
Turmoil bearings
An ideal potentiometer should have _______ resolution
Infinite
Sodium vapor lamp is also known as:
Cold cathode low pressure lamp
The transmission lines which feed different substations represent:
Primary distribution
For a non-linear system, is the Nyquist criterion applicable?
No
What is the value of air gap flux density in case of induction motor?
0.35 to 0.6 Wb/m²
In resistance welder, pneumatic pressure is applied during:
Squeeze, weld, and hold time
For which shape of conductors, the corona loss will be least?
Circular
The field flux of a dc motor can be controlled to get The speed higher than rated speed. True or False?
True
The capacitance of a transmission line is neglected up to:
200 km
The reason generating capacity which is available for resource but is not in operation is called:
Hot reserve
When analogy is drawn between electrical system and thermal system, current is considered analogous to:
Heat flow rate
Radiant efficiency of the luminous source depends on:
Temperature of the source
When does hunting take place in synchronous motor?
When load is variable
What happens if the choking coil of an operating florescent lamp is short circuited?
The current becomes so large that it damages the lamp.
What is the function of the surge tank in the hydropower plant?
Relieve water hammer pressures in the penstock pipe
According to second law of electrostatics, the force exerted between two-point charges Is directly proportional to the __________
product of their strengths
The charging current in transmission line _____ the voltage by ______
Leads, 90°
For dc shunt motor, speed controlled by the variation of field flux is best suited for:
Constant power drive
Hot template curves are plots of:
Conductor sage and span lengths
The economic size of a conductor is determined by what law?
Kelvin`s law
In control systems, what is the effect of the second derivative input signal?
Modify the time constant
On what factor does the back emf of synchronous motor depends?
Rotor excitation
Current chopping mainly occurs in which circuit breaker?
Air plant circuit breaker
What must be the brush shift angle in a dc machine interpole to get improve commutation?
Must be varied with the change in load
Lenz’s law is a consequence of the law of conservation of:
Energy
Plugging of dc motors is generally executed by reversing of:
Armature polarity
The highest value of thermal conductivity is for:
Solid ice
What is the required condition for running two alternators in parallel?
Terminal voltage should be same
In control systems, an increase in gain leads to:
Smaller damping ratio
A gas turbine works as:
Brayton cycle
For a second order differential equation if the damping ratio is 1, then the poles are:
are equal, negative and real
Alternator works on the principle of:
Faraday`s law of electromagnetic induction
Hydraulic torque transmission is analogous to:
Motor generator set
The steady state torque required to drive the motor and the load at synchronous speed is:
Synchronous
If a system has only two poles, then its damping ratio is:
Nonzero
The total connected load and number of points on a power sub-circuit should not exceed:
2000 W and 2 points respectively
The system having signal pole at the origin is:
Type – 1 system
Cylindrical pole type rotors are generally used with prime movers of:
High speed
Under force-current analogy, displacement is analogous to:
Magnetic flux linkage
What is the minimum permissible size of aluminum cable for power circuits?
3.5 sq cm
For underdamped second order system, the poles are:
Complex conjugates with negative real parts
A Diesel engine consumes diesel oil nearly at a rate of:
180 to 200 gm/BHP hr
The underground cable system for 11 kV can work up to a length of:
100 miles
A material that can be permanently magnetized is generally said to be:
Ferromagnetic
For a certain magnetic material, the ____ the area inside the hysteresis loop, the ____ the hysteresis losses.
greater, larger
Which of the following is the typical range of ferrite (a nonmetallic ferromagnetic material) relative permeability?
50 to 200
Ferrites are nonmetallic but have the ferromagnetic properties of iron. Ferrites are made of what material?
Ceramic
What coordinate system is often used to display the phase angle of a circuit containing resistance, inductive and/or capacitive reactance?
Polar coordinates
A potentially lethal electric current is on the order of:
0.1 A
What are the typical efficiencies of the transformers encountered in electronic circuits?
80 % to 90 %
What capacitors are found mainly in SMD form and are used extensively in RF and microwave circuits?
Porcelain capacitors
There are four classes of capacitors from Class 1 to Class 4. What is the relation between class number and capacitor performance?
The lower the class number the better the performance
A backward-working electric motor is best described as:
An electric generator
In the code for Class 1 dielectrics, what symbol is used to indicate the significant figures of the temperature coefficient in ppm/°C?
First symbol
What can you describe the maximum flux produced in the core of a transformer?
It is inversely proportional to supply frequency
At what load condition a transformer will have zero efficiency?
At no-load.
A transformer is so designed that primary and secondary windings have what coupling?
Tight magnetic coupling
Which motor never use belt-connected loads?
Series
In what application commutatively compounded motors are used?
Where sudden heavy loads for short duration is required.
An RLC series circuit, connected to a source E, is at resonance. Then the voltage across R equals the ______.
applied voltage
Iron, rather than copper, is used in the core of transformers because iron has a very high_______.
permeability
Of the three chief kinds of magnetic materials (diamagnetic, paramagnetic and ferromagnetic), which are used to make permanent magnets?
Only ferromagnetic
In which of the following voltage regulators the effect of dead zero is found?
Electromagnetic type
A square pulse has a mark-to-space ratio of _____.
1:1
When permanent magnet is strongly heated:
It loses its magnetism.
Before illuminating a P-N junction photodiode, it has to be ________.
reverse-biased
Light from any ordinary source (such as a flame) is usually:
Unpolarized
Maxwell-Wien Bridge is used for measuring __________.
inductance
The primary and secondary induced emf’s E₁ and E₂ in a two-winding transformer are always in-phase with each other. True or False?
True
The main function of an equalizer bar is to make the parallel operation of two over-compounded dc generators ______.
stable
In a three-phase Y-Y transformer connection, neutral is fundamental to the _________.
suppression of harmonics
In practice, earth is chosen as a place of zero electric potential because it:
Has almost constant potential.
If a self-excited dc generator after being installed, fails to build up on its first trial run, the first thing to do is ____________.
reverse field connections
The sediment which accumulates at the bottom of a lead-acid battery consists largely of:
Antimony-lead alloy
The kWh meter can be classified as a/an _______ instrument.
recording
Regarding skewing of motor bars in a squirrel-cage induction motor, which statement is false?
It increases starting torque.
The positive and negative halves of a complex wave are symmetrical when:
It contains odd harmonics.
No-load test on a transformer is carried out to determine _______.
magnetizing current and no-load loss
In a 3-ϕ induction motor, the rotor field rotates at synchronous speed with respect to _____.
stator
Surge absorbers protect against _____ voltage, ______ frequency oscillations.
low, high
During short-circuit test, the iron loss of a transformer is negligible because:
Flux produced is a small fraction of the normal flux.
The effect of increasing the length of air-gap in an induction motor will be to increase the _______.
magnetizing current
The main factor which loads to unstable parallel operation of flat- and over-compound dc generators is:
Their rising voltage characteristics.
All storage batteries have discharge limits, and nickel-cadmium, the type most used in hand-held portables, should not be discharged to less than:
1.0 volt per cell
A measure of the repeatability of a measurement of some quantity is:
Precision
A common germanium OA47 semiconductor diode is used for which of the following applications?
Signal detection
In a magnetic circuit, what losses are caused by reversing current direction thousands of times in a coil?
Hysteresis losses
If a right-handed bottle-opener cork screw is assumed to be along the conductor so as to advance in the direction of current flow, the motion of its handle will indicate the direction of magnetic flux produced around the conductor. This is known as ____ rule.
Cork screw
The ability of a mechanically stressed ferromagnetic wire to recognize rapid switching of magnetization when subjected to a dc magnetic field.
Wiegand effect
In all atoms, what force holds the electron in orbit?
Electrostatic force
In a magnetic circuit, what curve shows how much magnetic flux density results from increasing magnetic flux intensity?
BH magnetization curve
The maximum voltage output from a voltage divider:
Is equal to the supply voltage.
In __________ controllers the variable ac with fixed frequency is obtained
AC voltage
What rating of a DC generator is based on the mechanical limitation of the device used to turn the generator?
Power rating
The term _____ in electronics usually means the value of dc voltages for the device to operate properly.
bias
Who discovered the most important electrical effects which is the magnetic effect?
Hans Christian Oersted
A volume control in a stereo compact-disc player would probably be:
A logarithmic-taper potentiometer.
The permeability (µ) of a magnetic material is the ratio of B to H. The average value of permeability is measured where the ______ point is first established.
saturation or knee
In a magnetic circuit, what force must be applied in the reverse direction to reduce flux density to zero?
Coercive force
Suppose a certain current in a galvanometer causes the needle to deflect 20 degrees, and then this current is doubled. The needle deflection will ______.
increase
In a magnetic circuit, what lags behind the magnetizing force?
Magnetic flux
An electrical insulator can be made a conductor:
By ionizing it
For a type D chopper, if duty cycle = 0.5 then the Average voltage is ______
zero
In an atom, the energy level of an electron is ______ to its distance from the nucleus.
proportional
Which popular semiconductor diode is a low-voltage rectifier diode?
IN4001
The process of commutating a SCR by applying a reverse voltage to an SCR through a previously charged capacitor is called as:
Voltage commutation
If an electron has zero orbital angular momentum, the magnitude of its magnetic dipole moment equals:
a Bohr magneton
In active filter designs, what element or component is not needed?
Inductor
Maxwell’s great contribution to electromagnetic theory was his hypothesis that:
A time-varying electric flux acts as a current for purposes of producing a magnetic field
The increased conductivity of an illuminated semiconductor.
photoconductivity
One advantage of an electromagnet meter over a permanent-magnet meter is that:
The electromagnet meter is more rugged.
What is the ratio of the input impedance with series feedback to that without feedback?
1 + βA
Sequence control of ac voltage controllers is employed for the improvement of:
system power factor
In filters, what frequency is equivalent to the cut-off frequency (the point where the input-to-output power is reduced by one-half?
– 3 dB frequency
What transformer type is used in power supplies requiring a large core size?
Mains transformer
Drift current in the semiconductors depends upon:
Both the electric field and carrier concentration
The conversion of light to electrical energy.
photovoltaic effect
Silica is NOT a constituent for making porcelain insulators. True or False?
True
In a dc 3-wire distribution system, balancer fields are cross-connected in order to equalize voltages on the positive and negative outers. True or False?
True
Consider the following statements: 1. Resistor dissipates energy 2. Capacitor stores energy 3. Inductor dissipates energy Which of the above is/are correct?
1 and 2
Two parallel shunt generators will divide the total load equally in proportion to their kilowatt output ratings only when they have the same both rated ________ and ___________.
voltage, voltage regulation
The capacitor charging current is an exponential decay function. True or False?
True
The nodal method of circuit analysis is based on:
KCL and Ohm`s law
Which is an example of a variable renewable energy (VRE)?
Solar plant
Primary bushings is NOT a basic part of oil-type power transformer. True or False?
True
In a network made up of linear resistors and ideal voltage sources, values of all resistors are doubled. Then the voltage across each resistor is:
Not changed
Diesel electric traction has comparatively limited overload capacity because diesel engine is a constant-kW output prime mover. True or False?
True
In Kando system of track electrification, ______ is converted into _______.
1-phase ac, 3-phase dc
The topmost conductor in a high transmission line is _______.
earth conductor
A feeder, in a transmission system, feeds power to ______.
distributors
For the voltage build-up of a self-excited dc generator, total field circuit resistance must be less than the critical value. True or False?
False
Transmission line insulators are made of ______.
porcelain
The presence of ozone due to corona is harmful because it _______.
corrodes the material
The wooden poles well impregnated with creosite oil or any preservative compound have life ______.
25 to 30 years
For an overhead line, the surge impedance is taken as ______.
100 to 200 ohms
Shunt generators are most suited for stable parallel operation because of their voltage characteristics. Which one?
Dropping
By using bundles conductors power loss due to corona is reduced. True or False?
True
What method of heating is not dependent on the frequency of supply?
Electric resistance heating
A DC shunt motor is unsuitable for heavy duty starting. True or False?
False
Which instrument is used to measure high resistance as in the measurement of insulation resistance?
Megger
Conductors for high voltage transmission lines are suspended from towers to increase _______.
clearance from ground
Regenerative braking can be easily applied to _______motors
dc shunt
Magnetic materials are heated with the help of _______.
hysteresis loss
Why is the core losses are negligible during a short-circuit test conducted on transformer?
The mutual flux is small.
The electrostatic stress in underground cables is _______ at the conductor and ________ at the sheath
maximum, minimum
Which of the heating method is based on the transformer principle?
Induction heating
When a body reflects entire radiation incident on it, then it is known as:
White body
Irrespective of the supply frequency, the torque developed by a SCIM is the same whenever ________ is the same.
slip seed
The slight curvature at the lower end of the O.C.C. of a self-excited generator is due to ______.
high field circuit resistance
Skin effect is proportional to _______.
(conductor diameter)²
The effective disruptive critical voltage of a transmission line does not depend on ______.
material of the conductor
The square root of the ratio of line impedance and shunt admittance is called the _______.
surge impedance of the line
Load saturation characteristic of a dc generator gives relation between ______.
E_0 and I_f
Which of the distribution systems is more reliable?
Ring main system
For which of the following equipment current rating is not necessary?
Isolators
In a clockwise-rotating loaded dc generator, brushes have to be shifted:
clockwise
A 3-phase 4 wire system is commonly used on ______.
secondary distribution
The three factors which cause decrease in the terminal voltage of a shunt generator are
- armature reactances
- armature resistance
- armature leakages
- armature reaction
- reduction in field current
2, 4 and 5
The material commonly used for sheaths of underground cables is ______.
lead
By which of parameters is a busbar is rated?
Current, voltage, frequency and short time current
Constant voltage transmission entails that short-circuit current of the system is increased. True or False?
True
For aluminum, as compared to copper, all the following factors have higher values except _______.
electrical conductivity
When running under no-load condition and with normal excitation, armature current drawn by a synchronous motor ____ the applied voltage by a small angle
lags
The direction of rotation of a synchronous motor can be reversed by reversing the:
Supply phase sequence
Which of the following equipment, for regulating the voltage in distribution feeder, will be most economical?
Booster transformer
The frequency of voltage generated, in case of generators, can be increased by _______.
adjusting the governor
A Schrage motor is capable of behaving as a series motor. True or False
False
A synchronous condenser is generally installed at the ______ of the transmission line.
receiving end
If single-phasing of a 3-phase induction motor occur under running conditions, it may either stall or keep running depending on the load carried by it. True or False?
True
Series motor is not suited for traction duty due to current surges after temporary switching off supply. True or False?
True
What is the effect on current flow in reversing the direction of movement of a conductor in the magnetic field of a generator?
Reverse the direction of the current flow.
The area of cross-section of the neutral in a 3-wire dc system is generally _______ the area of cross-section of main conductor.
one-half
Which of the short-circuits is most dangerous?
Dead short-circuit
The customer is only charged or credited as the case may be, for the difference between the electricity supplied by the Distribution Utility and electricity it supplies to the Distribution Utility when the times it has excess VRE generation both of which are metered using either 2 bi-directional meter. What do you call this scheme?
Net Metering
The starting current of a transformer is generally _____ times of its rated full-load current.
6
The maximum value of torque angle a in a synchronous motor is _____ degrees electrical.
90
To use flywheel, motor should have ______.
drooping speed characteristics
Demand supply gap in power sector is expected to grow by ___ percent every year.
20
Rheostatic braking may be applied to an induction motor provided _______.
separate dc source for field excitation is available
When load on a normally-excited synchronous motor is increased, its power factor tends to ______.
become increasingly lagging
In electric traction, if contact voltage exceeds 1500 V, current collection is invariably via a ______.
overhead wire
Suspension insulators are used when transmission voltage is ______.
high
The ground ring transmission lines are used to _________.
reduce the earth capacitance of the lowest unit
The effect of wind pressure in power systems is more predominant on _______.
supporting the towers
Which of the following motors is preferred for traction work?
DC series motor
Which of the bar schemes is the most expensive?
Double bus-bar double breaker
A transformer has negative voltage regulation when its load power factor is _______.
leading
The material used for the manufacture of grounding wires is ________.
galvanized steel
For _______ lines, the excitation control method is satisfactory?
Short
Per system stability is least affected by:
Losses
The voltage drop, for constant voltage transmission, is compensated by installing ________.
synchronous motors
Which equipment should be installed by the consumers having low power factor?
Capacitor bank
In a substation this equipment is not installed:
Exciters
With which of the following are step-up substations associated?
Generating stations
Overhead lines generally use ______ conductors.
A.C.S.R.
Which of the following is the main disadvantage of AC transmission system over DC transmission system?
Less losses in transmission over long distances
The power factor of industrial loads is generally _______.
lagging
Unlike a shunt motor, it is difficult for a series motor to stall under heavy loading because _______.
it develops high overload torque
Under constant load conditions, the speed of a dc motor is affected by _______.
field flux
In performing the short circuit test of a transformer ______ side is usually short circuited :
Low voltage
Blocked rotor test on a 3-ϕ induction motor helps to find fixed losses. True or false?
False
In transmission lines, the cross-arms are made of ______.
steel
An ideal dc generator is one that has ________ voltage regulation.
zero
A tap changing transformer is used to step up as well as step down the voltage. True or False?
True
Which of the rotor quantities in a SCIM does not depend on its slip?
Speed
Between no-load and full-load, ______ motor develops the least torque.
series
At relatively light loads, transformer efficiency is low because fixed loss is _______in proportion to the output.
high
The main purpose of performing open circuit test on a transformer is to measure its _______.
core loss
The angular displacement between two interconnected stations is mainly due to ______.
reactance of the interconnector
High voltage transmission lines use _______ insulators.
suspension
In a 3-phase induction motor, the relative speed of stator flux with respect to ______ is zero.
rotor flux
A T-T connection has higher ratio of utilization than a V-V connection only when ______ transformers are used.
non-identical
The string efficiency of an insulator can be increased by correct grading of insulators of various capacitances. True or False?
True
The biggest advantage of T-T connection over the V-V connection for 3-phase power transformation is that it provides _______.
a true 3-phase, 4-wire system
In context of corona, if the conductors are polished and smooth, Corona glow will be uniform along the length of the conductor. True or False?
True
Out of the type of poles, which are bulky?
Concrete poles
The string efficiency of suspension insulators can be increased by both providing a guard ring and a true 3-phase, 4-wire system. True or False?
True
Which of the terminals in the power systems are connected by the service mains?
Distributor and consumer terminals
The current drawn by the line due to corona losses takes a _______ wave.
non-sinusoidal
The effect of ice on transmission line conductors is to increase the _______.
weight of the conductor
The effective resistance of a conductor will be the same as “ohmic resistance” when current is uniformly distributed in the conductor cross-section. True or False?
True
High voltage is primarily used, for long distance power transmission, to ______.
reduce the transmission losses
Transformers are rated in kVA instead of kW because total transformer loss depends on volt-ampere. True or False?
True
In the design of a distributor which of the following is the major consideration?
Voltage drop
When the amplitude of the oscillator in a series RLC circuit is doubled the current amplitude is:
doubled
A resistor, an inductor, and a capacitor are connected in parallel to a sinusoidal source of emf. The potential differences across all branches are in phase. True or False?
True
In a transmission system, if V is the transmission voltage, weight of copper needed is proportional to _______.
1/V²
When the frequency of the oscillator in a series RLC circuit is doubled the capacitive reactance is:
halved
In a transformer, electric power is transferred from primary coil to secondary by:
magnetic flux
The main reason that alternating current replaced direct current for general use is:
ac voltages may be conveniently transformed
Iron, rather than copper, is used in the core of transformers because iron:
has a very high permeability
By increasing the transmission voltage to double of its original value the same power can be dispatched keeping the line loss _______ of original value:
one fourth
Three phase step up transformer installed at power house, just before commencement of transmission line, have______ connection:
DELTA-STAR
