Basic Electricity Flashcards
The working voltage of a capacitor in an AC circuit should be
At least 50 percent greater than the highest applied voltage
Capacitors are sometimes used in DC circuits to
Smooth out slight pulsations in current/voltage
The term that describes the combined resistive forces in an AC circuit is
Impedance
What is the opposition to the flow of AC produced by an electromagnetic field (EMF) with generated back voltage called?
Inductive reactance
Electrostatic fields are also known as
Dielectric fields
The basis for transformer operation in the use of alternating current is mutual
Inductance
The opposition offered by a coil to the flow of alternating current is called (ignoring resistance) is called
Inductive reactance
What factors strengthen a coil inductor?
Adding coils close together
An increase in which of the following factors will cause an increase in the inductive resistance of a circuit?
Inductance and frequency
(Refer to figure 1.) When different rated capacitors are connected in series in a circuit, the total capacitance is
less than the capacitance of the lowest rated capacitor
Capacitors are sometimes used in DC circuits to
smooth out slight pulsations in current/voltage
In an AC circuit, the effective voltage is
less than the maximum instantaneous voltage
The amount of electricity a capacitor can store is directly proportional to the
plate area and inversely proportional to the distance between the plates
What is the total capacitance of a circuit containing three capacitors in parallel with capacitances of .02 microfarad, .05 microfarad and .10 microfarad?
.170uF
Convert farads to microfarads by
multiplying farads by 10 to the power of 6
Convert farads to picofarads by
multiplying farads by 10 to the power of 12
Unless specified, any values given for current or voltage in an AC circuit are assumed to be
effective values
When different rated capacitors are connected in parallel in a circuit, the total capacitance is
(Note: CT = C1 + C2 + C3…)
equal to the sum of all the capacitance
When inductors are connected in series in a circuit, the total inductance is (where the magnetic fields of each inductor do not affect the others) is
(Note: LT = L1 + L2 + L3…)
equal to the sum of the individual inductances
(Refer to figure 3.) When more than two inductors of different inductances are connected in parallel in a circuit, the total inductance is
less than the inductance of the lowest rated inductor
What is the total capacitance of a certain circuit containing three capacitors with capacitances of .25 microfarad, .03 microfarad and .12 microfarad?
.4 uF
Which requires the most electrical power during operation?
(Note 1 horsepower = 746 watts)
Two lights requiring 3 amperes each in a 24 volt parallel system
How much power must a 24-volt generator furnish to a system which contains the following loads?
450 watts
A 12 volt electric motor has 1,000 watts input and 1 horsepower output. Maintaining the same efficiency, how much input power will a 24 volt, 1 horsepower require?
(Note 1 horsepower = 746 watts)
1000 watts
How many amperes will a 28 volt generator be required to supply to a circuit containing five lamps in parallel, three of which have a resistance of 6 ohms each and two of which have a resistance of 5 ohms each?
25.53 amperes
A 24-volt, 1-horsepower DC electric motor that is 80 percent efficient requires 932.5 watts. How much power will a 12 volt, 1 horsepower DC electric motor that is 75 percent efficient require?
994.6 watts
The potential difference between two conductors which are insulated from each other is measured in
volts
Which effect does not apply to the movement of electron flowing in a conductor?
Static energy
A 24 volt source is required to furnish 48 watts to a parallel circuit consisting of four resistors of equal value. What is the voltage drop across each resistor?
24 volts
When calculating power in a reactive or inductive AC circuit, the true power is
less than apparent power
(Refer to figure 4.) How much power is being furnished to the circuit?
2,645 watts
(Refer to figure 5.) What is the impedance of an AC-series circuit consisting of an inductor with a reactance of 10 ohms, a capacitor with a reactance of 4 ohms, and a resistor with a resistance of 8 ohms?
10 ohms
(Refer to figure 6.) If resistor R5 is disconnected at the junction of R4 and R3 as shown as, what will the ohmmeter read?
3 ohms
(Refer to figure 7.) If resistor R3 is disconnected at terminal D, what will the ohmmeter read?
Infinite resistance
(Refer to figure 9.) How many instruments (voltmeters and ammeters) are installed correctly?
Two
The correct way to connect a test voltmeter in a circuit is
in parallel with a unit
What will a voltmeter read if properly connected across a closed switch circuit in a circuit with electrical power on?
Zero voltage
What does the letter Q symbolize when measuring electrical charge?
Coulombs
Which term means .001 amperes?
Milliamperes
A cabin entry light of 10 watts and a dome light of 20 watts are connected in parallel to a 30-volt source. If the voltage across the 10-watt light is measured, it will be
equal to the voltage across the 20-watt light
A 14-ohm resistor is to be installed in a series carrying .05 ampere. How much power will the resistor be required to dissipate?
At least 35 milliwatts
.002 kV equals
2.0 volts
(Refer to figure 64.) A 24 volt source is required to furnish 48 watts to a parallel circuit consisting of two resistors of equal value. What is the value of each resistor?
24 ohms
Which requires the most electrical power?
(Note 1 horsepower = 746 watts)
A 1/5 horsepower, 24 volt motor which is 75 percent efficient
What unit is used to express electrical power?
Watt
What is the basic unit of electrical quantity?
Coulomb
What is the operating resistance of a 30 watt light bulb designed for a 28 volt system?
26 ohms
When referencing resistance in a parallel DC circuit, which of the following statements is true?
The total current is equal to the sum of the currents through the individual branches of the circuit
Which of the following is commonly used as a rectifier in electrical circuits?
Diodes
Transfer of electrical energy from one circuit to another without the aid of electrical connections
is called induction
If three resistors of 3 ohms, 5 ohms and 22 ohms are connected in series in a 28 volt circuit, how much current will flow through the 3-ohm resistor?
0.93 amperes
A circuit has an applied voltage of 30 volts and a load consisting of a 10-ohm resistor in series with a 20-ohm resistor. What is the voltage drop across the 10-ohm resistor?
10 volt
In a parallel circuit with four 6-ohm resistors across a 24-volt battery, what is the total voltage across resistor-three (VR£) in the circuit?
24 volts
If each cell, connected in series, equals 2 volts, how would a 12-cell lead acid battery be rated?
24 volts
Which is correct in reference to electrical resistance?
If one of three bulbs in a parallel lighting circuit is removed, the total resistance of the circuit will become greater
What happens to the current in a voltage step up transformer with a ratio of 1 to 4?
The current is stepped down by an ratio of 1 to 4
In a parallel circuit with three 6-ohms resistors across a 12-volt battery, what is the total current value in the circuit?
6 amps
Which of these will cause the resistance of a conductor to decrease?
Decrease the length or increase the cross-sectional area
Bonding connections should not exceed
.003 ohms
Through which material will magnetic lines of force pass the most readily?
Iron
Which is correct concerning a parallel circuit?
Total resistance will be smaller than the smallest resistor
The voltage drop in a circuit of known resistance is dependant on
the amperage of the ciruit
A thermal switch, as used in a electric motor, is designed to
open the circuit in order to allow cooling of the motor
When referring to an electrical circuit diagram, what point is considered to be at zero voltage?
The ground reference
What is the purpose of the ground symbol used in electrical circuit diagrams?
To show that there is a return path for the current between the source of electrical energy and the load
In a P-N-P transistor application, the solid state device is turned on when the
base is negative with respect to the emitter
In an N-P-N transistor application, the solid-state device is turned on when the
base is positive with respect to the emitter
Typical application for zener diodes is as
voltage regulators
What two devices prevent a change in direction of current flow in a circuit under fault conditions?
Cut out replay and reverse current circuit breaker
Forward biasing of a solid state device will cause the device to
conduct
Which of the following logic gates will provide an active high out only when all inputs are different?
XOR
Which of the following logic gates will provide an active high out with all active high inputs?
AND
Which of the following logic gates provide a low output when any inputs are high?
NOR
A lead acid battery with 12 cells connected in series (no load voltage = 2.1 volts per cell) furnishes 10 amperes to a load of 2 ohms resistance. The internal resistance of the battery in this instance is
0.52 ohm
What is the no load voltage on a 6 cell battery capable of supplying 5 amperes?
12 volts
If electrolyte from a lead-acid battery is spilled in the battery compartment, which procedure should be followed?
Apply sodium bicarbonate solution to the affected area followed by a water rinse
Which statement regarding a hydrometer reading of a lead acid storage battery electrolyte is true?
The hydrometer reading does not require a temperature correction if the electrolyte temperature is 80F
A fully charged lead acid battery will not freeze until extremely low temperatures are reached because
most of the acid is in the solution
What determines the amount of current which will flow through a battery while it is being charged by a constant voltage source?
The state of charge of the battery
- Batteries of different voltages (but similar capacities) can be connected in series with each other across the charger and the charged using the constant current method
- Batteries of different ampere-hour capacity and same voltage can be connected in parallel with each other across the charger, and charged using the constant voltage method
Both No.1 and No.2 is true
The method used to rapidly charge a nickel-cadmium battery utilizes
constant voltage and varying current
The purpose of providing a space underneath the plates in a lead acid battery’s cell container is to
prevent sediment buildup from contacting the plates and causing a short circuit
Which condition is an indication of improperly torqued cell link connections of a nickel cadmium battery?
Heat or burn marks on the hardware
The presence of any small amounts of potassium carbonate deposits on the top of nickel-cadmium battery cells in service is an indication of
normal operation
What is the likely result if any, of servicing and charging of nickel cadmium battery and lead acid batteries together in the same service area?
Contamination of both types of batteries
The electrolyte of a nickel-cadmium battery is the lowest when the battery is
in a discharged condition
The electrolyte of a nickel-cadmium battery is the highest when the battery is
in a fully charged condition
The end-of-charge voltage of a 19-cell nickel-cadmium battery, measured while still on charge
depends upon its temp and the method used for charging
During discharge, nickel cadmium batteries will show a larger liquid level than when full charge because
the electrolyte become absorbed into the plates
How can the state-of-charge of a nickel-cadmium battery be determined?
By a measured discharge
What may result if water is added to a nickel-cadmium battery when it is not fully charged?
Excessive spewing is likely to occur during the charging cycle
In nickel cadmium batteries, a rise in cell temp
causes a decrease in internal resistance
Which of the following best describes the contributing factors to thermal runaway in a nickel-cadmium battery installed in a aircraft?
Low internal resistance intensified bt high cell temperature and a high current discharge/charge rate in a constant potential (voltage) charging system
When a charging current is applied to nickel cadmium battery, the cells emit gas
towards the end of the charging cycle
