Ch. 10 Flashcards
1
Q
- Ohm’s Law can be used to ________________________.
a. calculate current flow if the applied emf and resistance are known
b. calculate the required emf to cause a required current to flow through a known resistance
c. calculate the required circuit resistance if the voltage and current flow are known
d. All of the above
e. None of the above
A
d. All of the above
2
Q
- A DC circuit has 12 volts and a resistance of 300 ohms. The current flowing is___________.
a. 0.4 amps
b. 40 milliamps
c. 400 milliamps
d. 3600 amps
e. 25 milliamps
A
b. 40 milliamps
2
Q
- Circuit voltage is 24. Current is 10 amps. The resistance is ___________.
a. 240 ohms
b. 0.240 micro-ohms
c. 2.4 ohms
d. 0.416 ohms
e. 24 ohms
A
c. 2.4 ohms
3
Q
- According to Ohm’s Law __________________________.
a. if you raise E, I will go up
b. if you raise E, I will go down
c. if you raise R, I will go up
d. if you lower R, I will go down
e. if you raise I, R will go up
A
a. if you raise E, I will go up
3
Q
- If a light bulb in a circuit has a resistance of 100 ohms and 1 ampere of current flows in the circuit when the switch is closed, what is the voltage output of the battery?
a. 10 volts
b. 110 volts
c. 120 volts
d. 200 volts
e. 100 volts
A
e. 100 volts
4
Q
- If the resistance in a circuit was kept constant and the applied voltage was increased, there would be ______.
a. a corresponding decrease in current
b. no change in current
c. a corresponding increase in current
d. no change in resistance
e. a corresponding decrease in resistance
A
c. a corresponding increase in current
5
Q
- For a parallel circuit:
1) The same voltage is applied across all resistors
2) The current flow in each branch is directly proportional to the resistance in that branch
3) The total resistance of the parallel is always less than the smallest parallel resistance
4) The sum of the currents flowing in each path is equal to the supply current
a. 1, 2, 3
b. 2, 3, 4
c. 1, 2, 4
d. 1, 3, 4
e. 1, 2, 3, 4
A
d. 1, 3, 4
5
Q
- If the resistance of a circuit is decreased to 1/4 of its original value, what circuit change can be made to maintain the original circuit current?
a. The voltage would be 1/4 of original.
b. The voltage would be 4 times original.
c. The voltage would be 1/2 of original.
d. The voltage would remains constant.
e. The voltage would be doubled.
A
a. The voltage would be 1/4 of original.
6
Q
- If the resistance of a circuit is decreased to 1/4 of its original value, what happens to the current if the supply voltage is unchanged?
a. The current is 1/4 of original voltage.
b. The current remains the same.
c. The current is 1/2 of original voltage.
d. The current is 4 times its original voltage.
e. The current is 5 times its original voltage.
A
d. The current is 4 times its original voltage.
6
Q
- The quantity of current flow depends on _________________________.
a. the intensity of the emf
b. the conventional current flow
c. electron theory
d. the resistance in amps
e. the intensity of the resistance
A
e. the intensity of the resistance
7
Q
- A simple electric circuit consists of _________________.
a. source, load, resistance
b. conductor, load, source
c. current, resistance, conductor
d. voltage, current, conductor
e. voltage, inductance, conductance
A
b. conductor, load, source
7
Q
- According to Ohm’s Law _________________________.
a. if you raise I, R will go up
b. if you raise E, I will go down
c. if you raise R, I will go down
d. if you lower R, I will go up
e. if you raise E, I will go down
A
c. if you raise R, I will go down
7
Q
- Doubling both the voltage and resistance in a circuit has what effect on the current?
a. Current is doubled
b. Current is reduced by half
c. Current is reduced to 1/4
d. Current remains the same
e. Current is tripled
A
d. Current remains the same
8
Q
- Two lamps in a series circuit have equal and unknown resistance. Voltage is 220 and 2.75 amps. The resistance of each lamp is ____________.
a. 10 ohms
b. 80 ohms
c. 40 ohms
d. 30 ohms
e. 20 ohms
A
c. 40 ohms
9
Q
- In a Wheat stone bridge the applied voltage is 12 volts, resistance one is 800 ohms, resistance two is 500 ohms and resistance four is 300 ohms. Calculate the value in ohms of resistance three required to balance the bridge.
a. 400 ©
b. 480 ©
c. 450 ©
d. 300 ©
A
b. 480 ©
10
Q
- Wheatstone Bridge , where the applied voltage E = 24 V, R1 = 400 Ω, R2 = 500 Ω, and R4 = 200 Ω. Calculate the value of R3 required to balance the bridge.
a. 100 Ω
b. 250 Ω
c. 200 Ω
d. 160 Ω
A
d. 160 Ω
10
Q
- The power used by an electric heater drawing 5 amps at 110 volts is ______________.
a. 550 kilowatts
b. 55 watts
c. 22 watts
d. 550 watts
e. 550 Mega watts
A
d. 550 watts
10
Q
- When a Wheatstone bridge is balanced, the meter will read ______________________.
a. full scale positive
b. full scale negative
c. 100 percent
d. zero
e. 3/4 scale positive
A
d. zero
11
Q
- The measuring instrument used with a Wheatstone bridge circuit is a ______________.
a. Megger
b. Galvanometer
c. Ohm-meter
d. Ammeter
e. Voltmeter
A
b. Galvanometer
11
Q
- In the formula for work, W = EIT, the W equals ________.
a. Watts
b. Watt seconds
c. Watt hours
d. Watt joules
e. Watt minutes
A
b. Watt seconds
12
Q
- A Wheatstone bridge has R1 of 3000 ohms, R2 of 8000 ohms, R3 variable, and R4 of 15 ohms, the R3 would balance at __________.
a. 1.6 megohms
b. 40 ohms
c. 5.625 ohms
d. 56.25 ohms
e. 562.5 ohms
A
c. 5.625 ohms
12
Q
- The Wheatstone bridge accurately measures?
a. Resistances
b. Voltage
c. Watts
d. Current
e. Inductance
A
a. Resistances
13
Q
- An electric kettle is rated at 1500 W at 120 volts. The resistance would be _________.
a. 96 ohms
b. 12.5 ohms
c. 180 ohms
d. 24 ohms
e. 9.6 ohms
A
e. 9.6 ohms
14
Q
- The amount of energy in kilowatt-hours used by a 700-watt block heater in 6 hours is ___________.
a. 116.67 kWh
b. 4200 kWh
c. 175 kWh
d. 4.2 kWh
e. 42 kWh
A
d. 4.2 kWh
15
Q
- The power dissipated in a resistor is 60 watts at 110 volts. The resistance is ___________.
a. 6600 ohms
b. 201.66 ohms
c. 183.33 ohms
d. 32.73 ohms
e. 327.3 ohms
A
b. 201.66 ohms
16
Q
- Electric cost is 10 cents per kWh. Resistance is 10 ohms at 110 volts. Time is 2 hours. The cost is ________.
a. 22 cents
b. 12.1 cents
c. 11 cents
d. 24.2 cents
e. 26.2 cents
A
d. 24.2 cents
17
Q
- A resistor has a maximum loading current of 2 amps and a power rating of 1.5 watts. The resistance is _____.
a. 375 milliohms
b. 3 ohms
c. 0.75 ohms
d. 75 milliohms
e. 7.5 ohms
A
a. 375 milliohms
18
Q
- What is the frequency of a wave, which has a period of 2 µ sec?
a. 1.0 MHz
b. 0.25 MHz
c. 0.75 MHz
d. 0.5 MHz
A
d. 0.5 MHz
18
Q
- One-watt hour equals?
a. 3600 kJ
b. 3.6 kJ
c. 60 J
d. 36 MJ
e. 36 J
A
b. 3.6 kJ
19
Q
- The greatest instantaneous value of AC is ________________.
a. multitude
b. amplitude
c. two times the effective value
d. root-mean square
e. magnitude
A
b. amplitude
19
Q
- A 3-ohm resistor has a power rating of 1.5 watts. The maximum loading is ______________.
a. 0.707 amps
b. 0.05 amps
c. 4.5 amps
d. 20 amps
e. 22 amps
A
a. 0.707 amps
20
Q
- A lagging current means:
a. Voltage peaks before the current
b. The current is less than the voltage
c. The current peak precedes the voltage peak
d. Voltage and current are in phase
e. The residual current is less than the voltage
A
a. Voltage peaks before the current
21
Q
- For an AC circuit to be purely resistive, we must have:
1) No inductance
2) Current and voltage in phase
3) No capacitance
4) No lagging or leading current
a. 1, 2, 3
b. 2, 3, 4
c. 1, 2, 3, 4
d. 1, 3, 4
e. 1, 2, 4
A
c. 1, 2, 3, 4
21
Q
- In a purely inductive AC circuit the current ______________.
a. leads voltage by 90 degrees
b. is out of phase by 45 degrees
c. can lead or lag voltage
d. lags voltage by 90 degrees
e. is in phase with the voltage
A
d. lags voltage by 90 degrees
22
Q
- In a purely capacitive AC circuit the current _________________.
a. leads the voltage by 90 degrees
b. is out of phase by 45 degrees
c. can lead or lag voltage
d. lags voltage by 90 degrees
e. is in phase with voltage
A
a. leads the voltage by 90 degrees
23
Q
- If an ac voltage is applied to a circuit it will produce an ac current flow. If the voltage and the current reach their maximum values at the same time they are said to be ________.
a. out of phase
b. in phase
c. AC current
d. DC current
A
b. in phase
23
Q
- What is the period of a 60 Hz wave?
a. 0.02 sec
b. 0.018 sec
c. 0.016 sec
d. 0.01 sec
A
c. 0.016 sec
24
Q
- The root-mean-square value is:
1) 70.7% of the amplitude
2) 70.7% of the maximum instantaneous current
3) Termed the effective value
4) The amount of AC which will produce the same as a given amount of DC
a. 1, 2, 3
b. 2, 3, 4
c. 1, 3, 4
d. 1, 2, 4
e. 1, 2, 3, 4
A
e. 1, 2, 3, 4
25
Q
- What are the peak-to-peak and the maximum values of an alternating current if the rms value is 12 A?
a. 16.97 A, 33.94 A
b. 20.25 A, 45.55 A
c. 15.75 A, 30.15 A
d. 25.68 A, 50.55 A
A
a. 16.97 A, 33.94 A
25
Q
- The instantaneous maximum voltage is 135. The RMS value is __________.
a. 160 V
b. 95.45 V
c. 4 V
d. 339.46 V
e. 33.9 V
A
b. 95.45 V
25
Q
- The instantaneous maximum voltage is 240. The RMS value is ___________.
a. 160 V
b. 169.68 V
c. 4 V
d. 339.46 V
e. 33.9 V
A
b. 169.68 V
26
Q
- RMS current is 35 amps. The peak-to-peak value is ___________.
a. 24.75 amps
b. 49.5 amps
c. 70 amps
d. 99 amps
e. 9.9 amps
A
d. 99 amps
26
Q
- What are the peak-to-peak and rms values of voltage with a maximum value 170 V?
a. 300 V peak to peak, 100.05 V rms
b. 280 V peak to peak, 80.25 V rms
c. 340 V peak to peak, 120.19 V rms
d. 350 V peak to peak, 110.75 V rms
A
c. 340 V peak to peak, 120.19 V rms
27
Q
- What are the peak-to-peak and rms values of voltage with a maximum value of 311 V?
a. 550 V peak to peak, 210 V rms
b. 622 V peak to peak, 220 V rms
c. 650 V peak to peak, 235 V rms
d. 610 V peak to peak, 215 V rms
A
b. 622 V peak to peak, 220 V rms
28
Q
- A coil with an inductance of 0.2 H is connected to a 120 V, 60 Hz supply. Find:
(a) The inductive reactance of the coil.
(b) The current flowing through the coil.
a. (a) 70.0 ©, (b) 2.0 A
b. (a) 68.5 © , (b) 1.25 A
c. (a) 65 ©, (b) 1.05 A
d. (a) 75.4 ©, (b) 1.59 A
A
d. (a) 75.4 ©, (b) 1.59 A
28
Q
- What are the peak-to-peak and the maximum alternating current values if the rms current value is 20 A?
a. 25.22 A max., 55.00 A peak to peak
b. 30.25 A max., 62.75 A peak to peak
c. 28.29 A max., 56.57 A peak to peak
d. 35 A max., 65 A peak to peak
A
c. 28.29 A max., 56.57 A peak to peak
29
Q
- A coil has an inductance 20 mH. The inductive reactance is 100 Ω. Find the line frequency.
a. 750 Hz
b. 796 Hz
c. 722 Hz
d. 600Hz
A
b. 796 Hz
29
Q
- What current will flow when a 10 µF capacitor is connected to a 240 V, 60 Hz supply?
a. 1.25 A
b. 1.0 A
c. 0.9 A
d. 0.75 A
A
c. 0.9 A
30
Q
- A resistance of 50 Ω is connected in series with an inductive reactance of 70 Ω and a capacitive reactance of 20 Ω. What is the impedance of the circuit?
a. 70.71 Ω
b. 75 Ω
c. 65.21 Ω
d. 78.54 Ω
A
a. 70.71 Ω
31
Q
- What current will flow when a 10 µF capacitor is connected to a 120 V, 60 Hz power supply?
a. 0.075 A
b. 0.452 A
c. 0.0688 A
d. 0.124 A
A
b. 0.452 A
32
Q
- Impedance is_____________________________.
a. the combined effect of reactance and resistance
b. the lesser of capacitive reactance and inductive reactance
c. measured in ohms
d. current divided by voltage
e. the combined effect of inductance and conductance
A
a. the combined effect of reactance and resistance
32
Q
- A resistance of 60 Ω is connected in series with an inductive reactance of 50 Ω and a capacitive reactance of 40 Ω. What is the impedance of the circuit?
a. 75 Ω
b. 60.83 Ω
c. 65.02 Ω
d. 70.25 Ω
A
b. 60.83 Ω
32
Q
- Inductive reactance opposes ______________.
a. resistance
b. current flow
c. capacitance
d. voltage
e. conductance
A
b. current flow
33
Q
- The frequency of a wave having a period of 3 microseconds is _____________.
a. 6000 Hz
b. 33.33 MHz
c. 333.33 kHz
d. 600 Hz
e. 333.33 Hz
A
c. 333.33 kHz
34
Q
- A solenoid has 60 Hz supplied at 110 V and inductance of 0.6 H. The inductive resistance is:
a. 39 ohms
b. 226.08 ohms
c. 266.08 ohms
d. 39.60 ohms
e. 396 ohms
A
b. 226.08 ohms
35
Q
- A single-phase circuit has meter readings of 20 A, and 220 V. The power factor is 78.8%. Calculate:
(a) The real power of the circuit
(b) The imaginary power of the circuit
a. (a) 3200 W, (b) 2500 W
b. (a) 3250 W, (b) 2652 W
c. (a) 3467 W, (b) 2709 W
d. (a) 2859 W, (b) 2454 W
A
c. (a) 3467 W, (b) 2709 W
36
Q
- A solenoid has 60 Hz supplied at 110 V and inductance of 0.6 H. The current flowing is _________________.
a. 0.4866
b. 48.66 amps
c. 0.4866 amps
d. 48.66 milliamps
e. 4.866 amps
A
c. 0.4866 amps
37
Q
- The following meter readings were taken in an inductive single-phase circuit: wattmeter 2400 W; voltmeter 240 V; ammeter 15 A, frequency meter, 60 Hz. Note that a wattmeter indicates the active power and voltmeters and ammeters indicate effective (rms) values. Find:
(a) The apparent power (VA)
(b) The power factor of the circuit
a. (a) 3600 VA, (b) 67 %
b. (a) 2800 VA, (b) 65 %
c. (a) 2500 VA, (b) 70 %
d. (a) 3200 VA, (b) 62 %
A
a. (a) 3600 VA, (b) 67 %
38
Q
- The following meter readings were taken in an inductive single-phase circuit: wattmeter 2800W; voltmeter 120 V; ammeter 25 A, frequency meter, 60 Hz. Find:
(a) The apparent power
(b) The power factor
a. (a) 2500VA, (b) 90 %
b. (a) 2600 VA, (b) 91 %
c. (a) 3000 VA, (b) 93.3 %
d. (a) 3500 VA, (b) 95.5 %
A
c. (a) 3000 VA, (b) 93.3 %
39
Q
- There are two possible methods of connecting up three-phase generator windings. These are known as the _____ and the ______ connections.
a. advanced, simple
b. star, delta
c. temporary, permanent
d. tight, loose
A
b. star, delta
40
Q
- A three phase generator has a terminal voltage of 480 V and delivers full load current of 300 A per terminal at a lagging power factor of 75 percent. Calculate:
(a) The apparent power in kilovoltamperes
(b) The full load real power in kilowatts
a. (a) 252.25 kVA, (b) 192.88 kW
b. (a) 249.12 kVA, (b) 186.84 kW
c. (a) 260.55 kVA, (b) 200.78 kW
d. (a) 275.89 kVA, (b) 210.94 kW
A
b. (a) 249.12 kVA, (b) 186.84 kW
41
Q
- A three phase generator has a terminal voltage of 600 V and delivers full load current of 200 A per terminal at a lagging power factor of 80 percent. Find:
(a) The apparent power in kilovoltamperes
(b) The full load real power in kilowatts
a. (a) 252.25 kVA, (b) 192.88 kW
b. (a) 249.12 kVA, (b) 186.84 kW
c. (a) 260.55 kVA, (b) 200.78 kW
d. (a) 207.6 kVA, (b) 166.08 kW
A
d. (a) 207.6 kVA, (b) 166.08 kW
