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1 | |
In a capacitive circuit, the current delivered to a capacitor will rise to 63 percent of its maximum value after charging for a period of one time constant. |
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| | A) | True |
| | B) | False |
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2 | |
In an inductive circuit, the current decays to 37 percent of its initial value in a period of one time constant. |
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| | A) | True |
| | B) | False |
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3 | |
A capacitor with a breakdown voltage of 150 V would be safe to use in an ac circuit if the ac voltage were only 120 V |
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| | A) | True |
| | B) | False |
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4 | |
Capacitive reactance and inductive reactance increase with an increase in frequency of an alternating current. |
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| | A) | True |
| | B) | False |
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5 | |
The effective voltage V in a series ac circuit can be defined as the algebraic sum of VC, VL, and VR. |
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| | A) | True |
| | B) | False |
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6 | |
The power factor in an ac circuit is the ratio of its resistance to its impedance. |
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| | A) | True |
| | B) | False |
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7 | |
Under a condition of resonance in an ac circuit, the current will be in phase with the voltage. |
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| | A) | True |
| | B) | False |
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8 | |
Reactance, impedance, and resistance are all measured in the same physical unit (ohms). |
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| | A) | True |
| | B) | False |
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9 | |
In a circuit containing pure capacitance, the voltage leads the current by 90°. |
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| | A) | True |
| | B) | False |
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10 | |
A negative phase angle occurs when the current leads the voltage in an ac circuit. |
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| | A) | True |
| | B) | False |
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11 | |
The voltage of a circuit containing only inductive reactance |
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| | A) | is in phase with the current |
| | B) | leads the current by 90° |
| | C) | lags the current by 90° |
| | D) | leads the current by less than 90° |
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12 | |
An alternating voltage has a maximum value of 30 V. The effective value is approximately |
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| | A) | 15 V |
| | B) | 21.2 V |
| | C) | 30 V |
| | D) | 42.9 V |
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13 | |
As the capacitance in an ac circuit increases, the resonant frequency |
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| | A) | increases |
| | B) | decreases |
| | C) | remains the same |
| | D) | approaches zero |
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14 | |
The ratio of the pure resistance in an ac circuit to the impedance is known as the |
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| | A) | power factor |
| | B) | phase angle |
| | C) | resonant frequency |
| | D) | net reactance |
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15 | |
In a circuit containing pure capacitance, during a period of one time constant, the |
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| | A) | charge decays to 63 percent of its initial value |
| | B) | charge increases to 37 percent of its initial value |
| | C) | current decays to 37 percent of its initial value |
| | D) | capacitor is completely charged |
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16 | |
In an ac circuit containing a coil with an inductance of 0.3 H, the voltage is 120 V at 60 Hz. If we neglect resistance, the effective current in the coil is |
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| | A) | 0.27 A |
| | B) | 0.53 A |
| | C) | 1.06 A |
| | D) | 2.12 A |
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17 | |
A 50-Ω resistor, a 0.5-H inductor, and a 12- μF capacitor are connected in series with a 120-V, 60-Hz alternating current. The effective current is approximately |
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| | A) | 2 A |
| | B) | 4 A |
| | C) | 6 A |
| | D) | 8 A |
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18 | |
In Question 17, the power factor is |
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| | A) | 0.66 |
| | B) | 0.72 |
| | C) | 0.83 |
| | D) | 0.92 |
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19 | |
An 800-Ω resistor, a 0.6-H inductor, and a 4- μF capacitor are connected in series with a 220-V, 50-Hz source of alternating current. The phase angle is approximately |
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| | A) | -31° |
| | B) | -37° |
| | C) | 31° |
| | D) | 37° |
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20 | |
A circuit contains a 12-μF capacitor, a 40-Ω resistor, a switch, and a 20-V dc battery connected in series. After the switch is closed, the capacitor can be considered
fully charged after |
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| | A) | 0.00048 s |
| | B) | 0.0012 s |
| | C) | 0.0024 s |
| | D) | 0.0048 s |
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21 | |
One effective ampere is that alternating current that will develop the same as of direct current. |
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22 | |
In a(n) circuit, the current decays to 37 percent of its initial value in a period equal to one . |
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23 | |
In a capacitive circuit, the leads the , and the phase angle is . |
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24 | |
For an ac circuit containing capacitance, inductance, and resistance, the current will be a maximum when the frequency of the alternating voltage is equal to . |
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25 | |
The power factor is equal to the of the circuit divided by the . |
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26 | |
When the voltage and current reach maximum and minimum values at the same time, they are said to be . |
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27 | |
A given inductor has an inductance of one if an emf of one is induced by a current changing at the rate of one . |
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28 | |
In an inductive circuit, an increase in frequency of the applied voltage will the effective current. |
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29 | |
At resonant frequency, an ac circuit containing resistance, inductance, and capacitance acts as if it contained only . |
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30 | |
A household ac circuit has a 110-V, 60-Hz source of current. The actual voltage varies from to . |
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