Question 1

A series RLC circuit is driven by a 1.0-kHz oscillator. The circuit parameters are Vrms = 12 V, L = 5.0 mH, C = 4.0 μF, and R = 10 Ω. Under steady-state conditions, the rms potential difference across the resistor will be

Accepted Answer

A)  5.13 V. 
B)  9.19 V. 
C)  12.3 V. 
D)  14.7 V. 
E)  18.8 V.

Question 2

At what frequency is the reactance ) of a 2-mH inductor equal to the reactance ) of a 100-pF capacitor?

Accepted Answer

A)  2.2 × 106 Hz 
B)  1.3 × 1011 Hz 
C)  3.6 × 105 Hz 
D)  600 Hz 
E)  None of the above,

Question 3

You connect a 100-Ω resistor, a 800-mH inductor, and a 10.0-μF capacitor in series across a 60.0-Hz, 120-V peak) source. The approximate resonant frequency of your circuit is

Accepted Answer

A)  354 Hz. 
B)  60 Hz. 
C)  56 Hz. 
D)  37 Hz. 
E)  none of these is correct.

Question 4

At what frequency would the reactance ) of a 100-pF capacitor be 1000 Ω?

Accepted Answer

A)  3.18 MHz 
B)  15.9 MHz 
C)  1.59 MHz 
D)  3.98 MHz 
E)  2.54 Mhz

Question 5

A series RLC circuit is driven by a 1.0-kHz oscillator. The circuit parameters are Vrms = 12 V, L = 5.0 mH, C = 4.0 μF, and R = 10 Ω. Under steady-state conditions, the rms potential difference across the inductor will be

Accepted Answer

A)  5.13 V. 
B)  13.7 V. 
C)  21.9 V. 
D)  32.3 V. 
E)  47.2 V.

Question 6

If you double the frequency in the circuit shown, the inductive reactance  ) of the inductor

Accepted Answer

A)  increases by a factor of 2. 
B)  does not change. 
C)  decreases by a factor of 2. 
D)  increases by a factor of 4. 
E)  decreases by a factor of 4.

Question 7

Most calculators operate on 6.0 V. If, instead of using batteries, you obtain 6.0 V from a transformer plugged into 110-V house wiring, what must the ratio of the primary to the secondary turns be in the transformer? Ignore any changes in voltage due to rectification.)

Accepted Answer

A)  0.054 
B)  18 
C)  660 
D)  0.066 
E)  15

Question 8

A transformer is used to change

Accepted Answer

A)  capacitance. 
B)  frequency. 
C)  voltage. 
D)  power. 
E)  None of these is correct.

Question 9

A 5-μF capacitor is charged to 30 V and is then connected across a 10-μH inductor. The frequency of oscillation of the energy stored in the electric field of the capacitor and the magnetic field of the inductor is

Accepted Answer

A)  1.41 × 105 Hz 
B)  7.07 × 104 Hz 
C)  2.25 × 104 Hz 
D)  3.18 × 109 Hz 
E)  2.00 × 1010 Hz

Question 10

You connect a 250-Ω resistor, a 1.20-mH inductor, and a 1.80-μF capacitor in series across a 60.0-Hz, 120-V peak) source. The approximate impedance of your circuit is

Accepted Answer

A)  1.49 kΩ. 
B)  1.47 kΩ. 
C)  0.452 Ω. 
D)  250 Ω. 
E)  none of these is correct.

Question 11

The battery has a voltage V = 6 V, the inductance of the inductor L = 12 mH and the capacitance of the capacitor C = 8 mF. Assume that the inductor and the wires have zero resistance.The switch S was at position a for a long time when it is switched to b. What is the charge on the capacitor at t = 0.487 ms?

Accepted Answer

A)  0.75 μC 
B)  1.33 μC 
C)  48 μC 
D)  72 μC 
E)  zero

Question 12

As the frequency in this simple AC circuit increases, the rms power dissipated by the resistor

Accepted Answer

A)  increases. 
B)  does not change. 
C)  may increase or decrease depending on the magnitude of the original frequency. 
D)  may increase or decrease depending on the magnitude of the resistance. 
E)  decreases.

Question 13

A 500-W toaster is plugged into a 120-V AC outlet. What is the peak current in the toaster?

Accepted Answer

A)  0.24 A 
B)  4.2 A 
C)  2.9 A 
D)  0.34 A 
E)  5.9 A

Question 14

A circular coil with 20 turns and radius 5 cm is rotated in a uniform magnetic field of 3.2 T. If the maximum voltage induced in the coil is 5 V, calculate the number of rotations of the coil per minute.

Accepted Answer

A)  600 revs per minute 
B)  15 revs per minute 
C)  5 revs per minute 
D)  95 revs per minute 
E)  200 revs per minute

Question 15

The reactance ) of an inductor is 100 Ω at 2 kHz. The inductance of this inductor is

Accepted Answer

A)  1.99 mH. 
B)  3.98 mH. 
C)  7.96 mH. 
D)  8.86 mH. 
E)  None of these answers is correct.

Question 16

If you place a 40.0-μF capacitor across a generator that has a maximum EMF of 120 V, the capacitive reactance ) when the frequency is 60 Hz is approximately

Accepted Answer

A)  1.5 Ω. 
B)  66 Ω. 
C)  0.38 kΩ. 
D)  19 Ω. 
E)  0.13 kΩ.

Question 17

The battery has a voltage V = 6 V, the inductance of the inductor L = 12 mH and the capacitance of the capacitor C = 8 mF. Assume that the inductor and the wires have zero resistance.The switch S was at position a for a long time when it is switched to b. What is the charge on the capacitor at t = 0 s?

Accepted Answer

A)  0.75 μC 
B)  1.33 μC 
C)  48 μC 
D)  72 μC 
E)  zero

Question 18

A transformer is used in a converter so that a traveler can use a hair dryer made in the U.S. in their hotel room in Germany. The standard voltage in the U.S. is 120 V. The voltage in Germany is 220 V. The ratio of the number of turns must be

Accepted Answer

A)  0.545. 
B)  1.833. 
C)  20. 
D)  100. 
E)  340.

Question 19

At what frequency would the reactance ) of a 1.0-mH inductor be twice the reactance ) of a 10-μF capacitor?

Accepted Answer

A)  10 kHz 
B)  3.2 kHz 
C)  2.2 kHz 
D)  1.6 kHz 
E)  1.1 kHz

Question 20

How much does the maximum EMF produced by a generator a rotating coil) change if its magnetic field is halved?

Accepted Answer

A)  It is the same. 
B)  It is increased by a factor of 16. 
C)  It is decreased by a factor of 2. 
D)  It is increased by a factor of 4. 
E)  It is impossible to tell given the information provided.

Exam 21: Alternating-Current Circuits

A series RLC circuit is driven by a 1.0-kHz oscillator. The circuit parameters are V_rms = 12 V, L = 5.0 mH, C = 4.0 μF, and R = 10 Ω. Under steady-state conditions, the rms potential difference across the resistor will be