3A2 Chapter 10 Flashcards
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
D) all of the above
A DC circuit has 12 volts and a resistance of 300 ohms. The current flowing is _____
A) 0.4 amps B) 40 milliamperes C) 400 milliamperes D) 3600 amps E) 25 milliamperes
C) 40 milliamperes
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
C) 2.4 ohms
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) if you raise E, I will go up
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
E) 100 volts
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
C) a corresponding increase in current
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
E) the intensity of the resistance
If the resistance of a circuit is decreased by 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 its original
B) the voltage would be 4 times original
C) the voltage would be half the original
D) the voltage would remains constant
E) the voltage would be doubled
A) the voltage would be 1/4 of original
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 half of original voltage
D) the current is 4 times its original voltage
E) the current is 5 times its original voltage
D) the current is 4 times its original voltage
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
B) conductor, load, source
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
D) current remains the same
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
C) if you raise R, I will go down
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 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
D) 1,3,4
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
C) 40 ohms
In a Wheatstone bridge the applied voltage is 40 volts, resistance one is 350 ohms, resistance two is 250 ohms and resistance four is 100 ohms. Calculate the value in ohms of resistance three required to balance the bridge
A) 400 ohms
B) 480 ohms
C) 450 ohms
D) 300 ohms
B) 480 ohms
Wheatstone bridge, where the applied voltage E=24 V, R1=400 ohms, R2=500 ohms, and R4=200 ohms. Calculate the value of R3 required to balance the bridge
A) 100 ohms
B) 250 ohms
C) 200 ohms
D) 160 ohms
D) 160 ohms
The measuring instrument used with a Wheatstone bridge circuit is a ______
A) megger B) galvanometer C) ohm-meter D) ammeter E) voltmeter
B) galvanometer
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
D) zero
The Wheatstone bridge accurately measures?
A) resistances B) voltage C) watts D) current E) inductance
A) resistances
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
5.625 ohms
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 megawatts
D) 550 watts
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
E) 9.6 ohms
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
D) 4.2 kWh
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
B) 201.66 ohms
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) 375 milliohms
In the formula for work, W = EIT, W equals ____
A) watts B) Watt seconds C) Watt hours D) Watt joules E) Watt minutes
B) Watt seconds
One Watt hour equals \_\_\_\_\_\_\_ A) 3600 kJ B) 3.6 kJ C) 60 J D) 36 MJ E) 36 J
B) 3.6 kJ
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
D) 24.2 cents
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) 0.707 amps
The greatest instantaneous value of AC is _____
A) multitude B) amplitude C) two times the effective value D) root mean square E) magnitude
B) amplitude
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) voltage peaks before the current
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
C) 1,2,3,4
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
D) lags voltage by 90 degrees
In a purely capacitive 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) leads the voltage by 90 degrees
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
B) in phase
What is the period of a 60Hz wave?
A) 0.02 sec
B) 0.018 sec
C) 0.016 sec
D) 0.01 sec
C) 0.016 sec
What is the frequency of a wave, which has a period of 2 micro sec?
A) 1.0 MHz
B) 0.25 MHz
C) 0.75 MHz
D) 0.5 MHz
D) 0.5 MHz
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
E) 1,2,3,4
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
B) 169.68 V
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
B) 95.45 V
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
D) 99 amps
What are the peak to peak and RMS values of voltage with a maximum value of 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
C) 340 V peak to peak, 120.19 V rms
What are the peak to peak and the maximum values of an alternating current if the rms value is 12A?
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) 16.97 A, 33.94 A
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) 610V peak to peak, 215 V rms
B) 622 V peak to peak, 220 V rms
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
C) 28.39 A max,56.57 A peak to peak
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 c, b- 2.0 A
B) a- 68.5 c, b- 1.25 A
C) a- 65 c, b- 1.05 A
D) a- 75.4 c, b- 1.59 A
D) a- 75.4 c, b- 1.59 A
A coil has an inductance of 20 mph. The inductive reactance is 100 ohm. Find the line frequency
A) 750 Hz
B) 796 Hz
C) 722 Hz
D) 600 Hz
B) 796 Hz
What current will flow when a 10 uF 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
C) 0.9 A
A resistance of 50 ohm is connected in series with an inductive reactance of 70 ohm and a capacitive reactance of 20 ohm. What is the impedance of the circuit?
A) 70.71 ohm
B) 75 ohm
C) 65.21 ohm
D) 78.54 ohm
A) 70.71 ohm
What current will flow when a 10 uF capacitor is connected to a 120 V, 60 Hz power supply?
A) 0.75 A
B) 0.0452 A
C) 0.0688 A
D) 0.124 A
B) 0.0452 A
A resistance of 60 ohm is connected in series with an inductive reactance of 50 ohm and a capacitive reactance of 40 ohm. What is the impedance of the circuit?
A) 75 ohm
B) 60.83 ohm
C) 65.02 ohm
D) 70.35 ohm
B) 60.83 ohm
Inductive reactance opposes _________
A) resistance B) current flow C) capacitance D) voltage E) conductance
B) current flow
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) the combined effect of reactance and resistance
The frequency of a wave having a period o3 microseconds is _______
A) 6000 Hz B) 33.33MHz C) 333.33 KHz D) 600 Hz E) 333.33 Hz
C) 333.33 KHz
A solenoid has 60 Hz supplied at 110 V and inductance of 0.6 H. The inductive reactance is:
A) 39 ohms B) 226.08 ohms C) 266.08 ohms D) 39.60 ohms E) 396 ohms
B)226.08 ohms
A solenoid has 60 Hz supplied at 110 V and inductanceof 0.6 H. The current flowing is ________
A) 0.4866 B) 48.66 amps C) 0.4866 amps D) 48.66 milliamperes E) 4.866 amps
B) 48.66 amps
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
C) a- 3467 W, b- 2709 W
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- 3600 VA, b- 67%
The following meter readings were taken in an inductive single phase circuit: wattmeter 2800 W, voltmeter 120 V, ammeter 25 A, frequency meter 60 Hz. Find:
A) the apparent power
B) the power factor
A) a- 2500 VA, b- 90%
B) a- 2600 VA, b- 91%
C) a- 3000 VA, b- 93.3%
D) a- 3500 VA, b- 95.5%
C) a- 3000 VA, b- 93.3%
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
B) star, delta
A three phase generator has a terminal voltage
Rage 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
B) a- 249.12 kVA, b- 186.84 kW
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%. 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
D) a- 207.6 kVA, b- 166.08 kW
