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ELEX > REM A LVL 1, 2, & 3 > Flashcards

REM A LVL 1, 2, & 3 Flashcards

1
Q

When one of three series resistors is removed from a circuit and the circuit is reconnected, the current

A. increases by one-third
B. decreases by one-third
C. increases
D. decreases by the amount of current through the removed resistor

A

C. increases

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2
Q

Carbon-composition resistors:

A. Can handle lots of power.
B. Have capacitance or inductance along with resistance.
C. Work better for ac than for dc.
D. Are comparatively nonreactive.

A

D. Are comparatively nonreactive.

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3
Q

Good engineering practice usually requires that a series-parallel resistive network be made:

A. From resistors that are all the same
B. From a series combination of resistors in parallel
C. From resistors that are all very rugged
D. From a parallel combination of resistors in series

A

A. From resistors that are all the same

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4
Q

Two resistors are in parallel. Resistor A carries twice the current of resistor B, which means that:

A. the voltage across A is twice that across B
B. the voltage across B is twice that across A
C. A has half the resistance of B
D. B has half the resistance of A

A

C. A has half the resistance of B

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5
Q

A voltage across a series resistor circuit is proportional to?

A. The amount of time the circuit was on for
B. The power in the circuit
C. The value of the other resistances in the circuit
D. The value of the resistance itself

A

D. The value of the resistance itself

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6
Q

Red, red, red, gold indicates
A. 2.2 K ohms
B. 220 ohms
C. 22 ohms
D. 22 K ohms

A

A. 2.2 K ohms

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7
Q

In a mesh, the algebraic sum of all voltages and voltage drops is equal to zero.

A. Norton’s law
B. Kirchhoff’s first law
C. Superposition theorem
D. Kirchhoff’s second law

A

D. Kirchhoff’s second law

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8
Q

Mesh analysis is best used together with what circuit law?

A. VDT
B. CDT
C. KVL
D. KCL

A

C. KVL

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9
Q

The current flowing in the branches of a d.c. circuit may be determined using:

A. Kirchhoff’s laws
B. Faraday’s laws
C. Lenz’s law
D. Fleming’s left-hand rule

A

A. Kirchhoff’s laws

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10
Q

When applying KVL, a closed path is commonly referred to as

A. node
B. branch point
C. loop
D. principal node

A

C. loop

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11
Q

In a parallel circuit with a voltage source and several branch resistors, how is the total current related to the current in the branch resistors?

A. It decreases as more parallel resistors are
added to the circuit
B. It equals the average of the branch current
through each resistor
C. It is the sum of each resistors voltage drop
multiplied by the total number of resistors
D. It equals the sum of the branch current
through each resistor

A

D. It equals the sum of the branch current
through each resistor

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12
Q

Which of the following is also known as
the dual of Thevenin’s theorem?

A. Maximum power transfer theorem
B. Norton’s theorem
C. Superposition theorem
D. Millman’s theorem

A

B. Norton’s theorem

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13
Q

The primary method of analyzing a
circuit with two or more voltage sources
is usually

A. Kirchhoff’s law
B. Ohm’s law
C. Thevenin’s theorem
D. superposition

A

D. superposition

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14
Q

Norton’s theorem gives

A. an equivalent current source in parallel
with an equivalent impedance
B. an equivalent current source in series with
an equivalent impedance
C. an equivalent voltage source in parallel
with an equivalent impedance

A

A. an equivalent current source in parallel
with an equivalent impedance

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15
Q

A Thevenin equivalent circuit consists
of

A. a voltage source in series with a
resistance
B. two voltage sources and a resistance
C. a current source in parallel with a
resistance

A

A. a voltage source in series with a
resistance

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16
Q

The primary method of analyzing a
circuit with two or more voltage sources
is usually

A. superposition
B. Thevenin’s theorem
C. Kirchhoff’s law

A

A. superposition

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17
Q

Norton resistance is found by?

A. Shorting all voltage sources
B. Shorting all voltage sources and
opening all current sources
C. Opening all current sources
D. Opening all voltage sources and shorting
all current sources

A

B. Shorting all voltage sources and
opening all current sources

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18
Q

The Norton current is the ___

A. Open circuit and short circuit current
B. Open circuit current
C. Short circuit current

A

C. Short circuit current

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19
Q

Why would it be important to minimize
the mutual inductance between two
inductors?

A. To reduce unwanted coupling between
circuits
B. To reduce conducted emissions
C. To increase the energy transfer between
circuits

A

A. To reduce unwanted coupling between
circuits

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20
Q

A series connected C -R circuit is
suddenly connected to a d.c. source of
V volts. Which of the statements is
false?

A. The initial voltage drop across the resistor
is IR, where I is the steady-state current
B. The capacitor voltage is equal to the
voltage drop across the resistor
C. The voltage drop across the resistor
decays exponentially
D. The initial capacitor voltage is zero

A

B. The capacitor voltage is equal to the
voltage drop across the resistor

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21
Q

A material with a high dielectric
constant:

A. Acts to increase capacitance per unit
volume
B. Has no effect on capacitance
C. Causes a capacitor to become polarized

A

A. Acts to increase capacitance per unit
volume

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22
Q

Inductors in series, assuming there is no
mutual inductance, combine:

A. Like resistors in series
B. In a way unlike any other type of
component
C. Like resistors in parallel

A

A. Like resistors in series

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23
Q

The capacitance of a capacitor is the
ratio

A. Charge to potential difference between
plates
B. Potential difference between plates to
thickness of dielectric
C. Potential difference between plates to
plate spacing

A

A. Charge to potential difference between
plates

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24
Q

The effect of inductance occurs in an
electrical circuit when:

A. none of these choices
B. the current is changing
C. the flux is changing
D. the resistance is changing

A

B. the current is changing

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25
Q

If you have light bulbs marked 40 watts,60 watts and 100 watts, which one will use electrical energy the fastest?

A. The 60 watt bulb
B. The 40 watt bulb
C. The 100 watt bulb

A

C. The 100 watt bulb

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26
Q

In a series-connected string of holiday
ornament bulbs, if one bulb gets
shorted out, which of these is most
likely?

A. The current in the string will stay the same.
B. All the other bulbs will go out.
C. The current in the string will go up.

A

C. The current in the string will go up.

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27
Q

If you measure all the voltage drops and the source voltage in a series circuit and add them together, taking into
consideration the polarities, you will get
a result equal to

A. the source voltage
B. the total of the source voltage and the
voltage drops
C. zero

A

C. zero

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28
Q

Electrical current is measured in which
of the following units?

A. Ohms
B. Amperes
C. Volts

A

B. Amperes

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29
Q

What must be known in order to calculate the energy used by an electrical appliance?

A. current and time of operation
B. power and time of operation
C. current and resistance

A

B. power and time of operation

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30
Q

How is the current in a DC circuit calculated when the voltage and resistance are known?

A. Current equals voltage divided by
resistance
B. Current equals power divided by voltage
C. Current equals resistance multiplied by voltage
D. Current equals resistance divided by
voltage

A

A. Current equals voltage divided by
resistance

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31
Q

What is the basic unit of electrical
power?

A. The ampere
B. The watt
C. The volt
D. The ohm

A

B. The watt

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32
Q

The effect of connecting an additional
parallel load to an electrical supply
source is to increase the

A. resistance of the load
B. p.d. across the load
C. current taken from the source
D. voltage of the source

A

C. current taken from the source

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33
Q

What is the zero-voltage switch used
for?

A. To control low-voltage circuits
B. To reduce radiation of high frequencies
during turn-on of a high current to a
load
C. For extremely low-voltage applications
D. To provide power to a circuit when power
is lost

A

B. To reduce radiation of high frequencies
during turn-on of a high current to a
load

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34
Q

Which of the following statements is
false?

A. Current is at a maximum at resonance in
an a.c. circuit
B. Apparent power÷True power gives
power factor
C. The product of r.m.s. current and voltage
gives the apparent power in an a.c. circuit

A

B. Apparent power÷True power gives
power factor

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35
Q

A series connected C -R circuit is
suddenly connected to a d.c. source of
V volts. Which of the statements is
false?

A. The time constant of the circuit is given by
CR
B. The final value of the current is zero
C. The current grows exponentially

A

C. The current grows exponentially

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36
Q

Which of the following is a reason not to
use wire-wound resistors in an RF
circuit?

A. The resistor’s tolerance value would not be
adequate for such a circuit
B. The resistor’s inductance could make
circuit performance unpredictable
C. The resistor could overheat
D. The resistor’s internal capacitance would
detune the circuit

A

B. The resistor’s inductance could make
circuit performance unpredictable

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37
Q

What device can be used to minimize
the effect of RF pickup by audio wires
connected to stereo speakers, intercom
amplifiers, telephones, etc.?

A. Diode
B. Magnet
C. Ferrite core

A

C. Ferrite core

38
Q

The most useful ac bridge for
comparing capacitances of two air
capacitors is _bridge.

A. Schering
B. De Sauty
C. Wien parallel
D. Wien series

A

B. De Sauty

39
Q

Hay’s bridge is particularly useful for
measuring.

A. Self inductance
B. Mutual inductance
C. Inductive impedance with large phase
angle

A

C. Inductive impedance with large phase
angle

40
Q

As frequency increases.

A. series RC impedance increases and
parallel RC impedance decreases
B. series RC impedance decreases and
parallel RC impedance increases
C. both series and parallel RC impedance
decrease

A

C. both series and parallel RC impedance
decrease

41
Q

When the frequency of an a.c. circuit
containing resistance and inductance is
increased, the phase angle of the circuit

A. increases
B. stays the same
C. decreases

A

A. increases

42
Q

Each impedance R +jXL:

A. All of these choices
B. Corresponds to a unique point in the RL
plane.
C. Corresponds to a unique resistance.
D. Corresponds to a unique inductive
reactance.

A

A. All of these choices

43
Q

When the resistor voltage in a series RL circuit becomes less than the inductor voltage, the phase angle

A. cannot be determined
B. decreases
C. is not affected
D. increases

A

D. increases

44
Q

If the dielectric material between the plates of a capacitor is changed, all other things being equal:

A. The value of Xc decreases negatively.
B. The value of Xc does not change.
C. You can’t say what happens to XC
without more data.

A

C. You can’t say what happens to XC
without more data.

45
Q

In the complex plane, the number 14-
j5 is located in the

A. first quadrant
B. third quadrant
C. fourth quadrant
D. second quadrant

A

C. fourth quadrant

46
Q

In a Y-connected circuit, the magnitude
of each line current is

A. three times the corresponding phase
current
B. equal to the corresponding phase
current
C. zero

A

B. equal to the corresponding phase
current

47
Q

What should be the impedance of a low
pass filter as compared to the
impedance of the transmission line into
which it is inserted?

A. Twice the transmission line impedance
B. About the same
C. Substantially higher

A

B. About the same

48
Q

If the resistance in parallel with a
parallel resonant circuit is reduced, the
bandwidth

A. increases
B. decreases
C. becomes sharper

A

B. decreases

49
Q

Power factor is equal to:

A. True power divided by apparent power
B. Apparent power divided by true power
C. Imaginary power divided by true power

A

A. True power divided by apparent power

50
Q

Parallel tuned circuits offer:

A. low impedance at resonance
B. very high impedance at resonance
C. an impedance equal to resistance of the
circuit

A

B. very high impedance at resonance

51
Q

When a series LCR circuit is tuned to the
frequency of the source, the:

A. line current leads the applied voltage
B. impedance is maximum
C. line current reaches maximum

A

C. line current reaches maximum

52
Q

How many types of power can be
defined in an AC circuit?

A. 3
B. 1
C. 5
D. 2

A

A. 3

In an AC circuit, we can define three
types of power, namely, Instantaneous
power, Average power, and Apparent
power.

53
Q

What is the power factor in a pure
resistive circuit?

A. 0
B. Infinity
C. 1
D. -1

A

C. 1

A circuit containing only a pure
resistance in an AC circuit is known as a
pure resistive AC Circuit. For a purely
resistive circuit, the power factor is one,because the reactive power equals zero, i.e.

Φ=0- Power factor (cos0)=1

54
Q

What is the power factor in a pure
inductive or capacitive circuit?

A. 0
B. -1
C. Infinity

A

A. 0

A circuit which contains only inductance
is called a pure inductive circuit and a
circuit containing only a pure capacitor is known as a pure capacitive circuit. In a pure inductive circuit or a pure
capacitive circuit, the current is lagging
or ahead by 90 degrees from the
voltage. The power factor is the cosine
of the angle between the voltage and
the current. Therefore:
Φ=π2 - Power factor (cosn2)=0

55
Q

Which of the following is true about
power factor?

A. cosΦ = True power /Apparent power
B. cosΦ = Apparent power/ True power
C. sinΦ = True power / Apparent power

A

A. cosΦ = True power /Apparent power

The power factor of an AC electrical
power system is defined as the ratio of the real or true power absorbed by the load to the apparent power flowing in the circuit, and in the closed interval of
-1 to 1. The expression for power factor
is given as: cosΦ = True power / Apparent power

56
Q

Power factor of an inductive circuit is
usually improved by adding a capacitor
to it in

A. Either series or parallel
B. None of these choices
C. Parallel
D. Series

A

A. Either series or parallel

57
Q

For a given wirewound core, an increase
in current through the coil

A. increases the flux density
B. decreases the flux density
C. reverses the flux lines
D. causes no change in flux density

A

A. increases the flux density

58
Q

When the speed at which a conductor is
moved through a magnetic field is
increased, the induced voltage

A. reaches zero
B. remains constant
C. decreases
D. increases

A

D. increases

59
Q

What are the effects of moving a closed
wire loop through a magnetic field?

A. A current is induced in the wire
B. All of these choices
C. The polarity across the wire depends on
the direction of motion.
D. A voltage is included in the wire

A

B. All of these choices

60
Q

If a conductor is horizontal, the current
flowing from left to right and the
direction of the surrounding magnetic field is from above to below, the force exerted on the conductor is.

A. from left to right
B. towards the viewer
C. away from the viewer
D. from below to above

A

C. away from the viewer

61
Q

Magnetic flux can always be attributed
to:

A. Ferromagnetic materials
B. The geomagnetic field
C. Motion of charged particles

A

C. Motion of charged particles

62
Q

When the current through an inductor is cut in half, the amount of energy stored in the electromagnetic field?

A. doubles
B. does not change
C. is quartered
D. quadruples

A

C. is quartered

63
Q

Which of the following symbol denotes
magnetic field intensity?

A. B
B. mmf
C. H

A

C. H

B= flux density
mmf = magnetomotive force
H= magnetic field intensity

64
Q

Which of the following statements is/
are true?
P: hard magnetic material has high
remanence
Q: hard magnetic material has large
coercivity

A. Q only
B. neither P nor Q
C. P only
D. both P and Q

A

D. both P and Q

Hard magnetic material has high
remanence and large coercivity making
them difficult to demagnetize.

65
Q

What is the name for a non-metallic material that has the ferromagnetic properties of iron?

A. toroid
B. solenoid
C. ferrite
D. lodestone

A

C. ferrite

Ferrites are ceramic-like materials with magnetic properties that are useful in many types of electronic devices.

66
Q

Anderson bridge is a modification of ___ bridge.

A. Maxwell-Wien
B. Hay’s
C. Owen

A

A. Maxwell-Wien

67
Q

The force between a magnet and a
piece of ferromagnetic metal that has
not been magnetized:

A. Is never repulsive
B. Can be either repulsive or attractive
C. Gets smaller as the magnet gets closer to
the metal
D. Depends on the geomagnetic field

A

A. Is never repulsive

68
Q

What is the unit for relative
permeability?

A. No unit
D. H-m
C. H/m

A

A. No unit

Relative permittivity is a unitless
quantity since it is a ratio of
permeability and absolute permeability
that are both expressed in H/m.

69
Q

A permanent magnet would most likely
be made from:

A. brass
B. copper
C. aluminum
D. steel

A

D. steel

70
Q

The phenomenon of perfect
diamagnetism is called ___

A. Meissner Effect
B. Zero Kelvin Effect
C. Diamagnetic Effect
D. Superconductivity

A

A. Meissner Effect

The phenomenon of perfect
diamagnetism in superconductors is called the Meissner effect, after the name of its discoverer. It is used to magnetically levitate superfast trains.

71
Q

Which of the following statements about a three-phase squirrel-cage induction motor is false?

A. It has no external electrical connections to
its rotor
B. A magnetic flux which alternates is
produced
C. It has no external electrical connections to
its rotor
D. It is cheap, robust and requires little or no
skilled maintenance

A

B. A magnetic flux which alternates is
produced

72
Q

The slip speed of an induction motor:

A. is zero until the rotor moves and then rises
to 100 per cent
B. is 100 per cent until the rotor moves and
then decreases slightly
C. is 100 per cent until the rotor moves
and then falls to a low value

A

C. is 100 per cent until the rotor moves
and then falls to a low value

73
Q

Refer to a three-phase induction motor.
Which statements are false?

A. The slip speed is the synchronous speed
minus the rotor speed
B. The torque on the rotor is due to the
interaction of magnetic fields
C. As the rotor is loaded, the slip
decreases
D. The torque on the rotor is due to the
interaction of magnetic fields

A

C. As the rotor is loaded, the slip
decreases

74
Q

The slip speed of an induction motor
depends upon:

A. eddy currents
B. supply voltage
C. mechanical load

A

C. mechanical load

75
Q

Electric motors works on the principle of

A. couple
B. friction
C. capacitors
D. torque

A

D. torque

76
Q

The slip speed of an induction motor
may be defined as the:

A. number of pairs of poles ÷ frequency
B. rotor speed - synchronous speed
C. synchronous speed - rotor speed

A

C. synchronous speed - rotor speed

77
Q

How should the winding axes of
solenoid inductors be placed to
minimize their mutual inductance?

A. In line
B. At right angles
C. Parallel to each other
D. Interleaved

A

B. At right angles

78
Q

An LR-C parallel circuit has the
following component values: R = 100, L= 10mH,C=10 μF and V= 100 V. Which of the following statements is false?

A. The circuit Q-factor at resonance is 30
B. The dynamic resistance is 1000
C. The current at resonance is 1A
D. The resonant frequency fr is 1.5/π kHz

A

A. The circuit Q-factor at resonance is 30

79
Q

In a highly capacitive circuit

A. Reactive power is more than the apparent
power
B. Apparent power is equal to the actual
power
C. Reactive power is more than the actual
power
D. Actual power is more than its reactive
power

A

C. Reactive power is more than the actual
power

80
Q

What is the power factor for a series
LCR circuit at resonance?

A. -1
B. Infinity
C. 1

A

C. 1

At resonance, XL=Xc →Z=R;
So, the total impedance of the circuit is
only due to resistor. The phase angle
between voltage and current is zero.
Therefore, Φ=OPower factor (cosΦ)=1

81
Q

Pure inductive circuit

A. Does not take power at all from a line
B. Takes power from the line during some part of the cycle and then returns back to it during other part of the cycle
C. None of these choices

A

B. Takes power from the line during some part of the cycle and then returns back to it during other part of the cycle

82
Q

In AC circuit the power curve is a sine
wave having

A. Three times the frequency of the voltage
B. Same frequency as that of voltage
C. Double the frequency of voltage

A

C. Double the frequency of voltage

83
Q

The power factor of practical inductor is

A. Unity
B. Leading
C. Lagging
D. Zero

A

C. Lagging

84
Q

When an alternating current passes
through an ohmic resistance the
electrical power converted into heat is

A. True power
B. None of these choices
C. Reactive power

A

A. True power

85
Q

A material that can be permanently
magnetized is generally said to be.

A. Ferromagnetic.
B. Magnetic.
C. Permanently magnetic.
D. Electromagnetic.

A

A. Ferromagnetic.

86
Q

For the circuit shown in the figure, the
internal resistance r is given by:

(REM A ELEX LVL 1,2,3 FIGURE)

A. 1/E-V
B. I/V-E
C. V-E/I
D. E-V/I

A

C. V-E/I

87
Q

The only inductive circuit takes power
from the AC mains when

A. Applied voltage decreases but current
increases
B. Both applied voltage and current decrease
C. Applied voltage decreases but current
decreases

A

A. Applied voltage decreases but current
increases

88
Q

A pure capacitance is connected across 50 HZ, 230 V supply consumes 0.04 W.This consumption is attributed to

A. Ohmic loss due to ohmic resistance of
plates
B. Loss of energy in dielectric
C. Both Ohmic loss due to ohmic resistance
of plates and Loss of energy in dielectric
D. Capacitive reactance in ohms

A

A. Ohmic loss due to ohmic resistance of
plates

89
Q

An alternator is delivering power to a
balanced load at unity power factor. The
phase angle between the line voltages
and the line current is

A. 0°
B. 60°
C. 30°

A

C. 30°

90
Q

In a three-phase supply, floating neutral
is undesirable because it may result
in…….across the load.

A. None of these Choices
B. High voltage
C. Unequal line voltages

A

C. Unequal line voltages

91
Q

The power factor of an ordinary electric
bulb is

A. Unity
B. Slightly more than unity
C. Zero
D. Slightly less than unity

A

D. Slightly less than unity

92
Q

To improve the power factor in three phase circuits, the capacitor bank is connected in Delta to make

A. The power factor correction more effective
B. The connection elegant
C. Capacitance very small

A

C. Capacitance very small

ELEX (13 decks)

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