Question 1

An electric motor produces 2.0 hp in a Vrms = 120 V circuit. Using 1 hp = 746 W, how long would it take this motor to do 1.0 kWh of work?

Accepted Answer

A)  0.67 min 
B)  0.67 h 
C)  1.3 min 
D)  1.3 h 
A)  0.67 min 
B)  0.67 h 
C)  1.3 min 
D)  1.3 h

Question 2

The rms current is equal to the direct current that:

Accepted Answer

A)  produces the same average voltage across a resistor as in an AC circuit. 
B)  provides the same average current in a resistor as in an AC circuit. 
C)  results in the same peak power in a resistor as in an AC circuit. 
D)  dissipates an equal amount of energy in a resistor at the same rate as in an AC circuit. 
A)  produces the same average voltage across a resistor as in an AC circuit. 
B)  provides the same average current in a resistor as in an AC circuit. 
C)  results in the same peak power in a resistor as in an AC circuit. 
D)  dissipates an equal amount of energy in a resistor at the same rate as in an AC circuit.

Question 3

An FM radio tuning circuit has a coil with an inductance of 0.0015 mH. What is the value of the capacitance if the set is tuned to 98 MHz?

Accepted Answer

A)  1.8 *10-6 $\mu$F 
B)  0.88 *10-6$\mu$F 
C)  0.98 *10-6 $\mu$F 
D)  12 *10-6 $\mu$F 
A)  1.8 *10-6 $\mu$F 
B)  0.88 *10-6$\mu$F 
C)  0.98 *10-6 $\mu$F 
D)  12 *10-6 $\mu$F

Question 4

A series LC circuit in a radio is in resonance with AM 1200 kHz. If the radio station is changed to AM 600 kHz, by what factor must the capacitance be multiplied to again achieve resonance?

Accepted Answer

A)  4 
B)  2 
C)  1/2 
D)  1/4 
A)  4 
B)  2 
C)  1/2 
D)  1/4

Question 5

Find the resonant frequency for a series LCR circuit where R = 20.0 $\Omega$, C = 10.0 µF, and L = 8.0 mH.

Accepted Answer

A)  1.59 kHz 
B)  563 Hz 
C)  5.00 kHz 
D)  796 Hz 
A)  1.59 kHz 
B)  563 Hz 
C)  5.00 kHz 
D)  796 Hz

Question 6

An AM radio tuning circuit has a coil with an inductance of 4.00 mH and a capacitor set at 7.50 *10-6 $\mu$F. What frequency will it detect?

Accepted Answer

A)  1520 kHz 
B)  919 kHz 
C)  550 kHz 
D)  750 kHz 
A)  1520 kHz 
B)  919 kHz 
C)  550 kHz 
D)  750 kHz

Question 7

A transformer is to be designed to increase the 30 kV (rms) output of a generator to the transmission line voltage of 345 kV (rms). If the primary winding has 60 turns, how many turns must the secondary have?

Accepted Answer

A)  57 
B)  6900 
C)  690 
D)  11 
A)  57 
B)  6900 
C)  690 
D)  11

Question 8

If the rotating coil used in a generator has its radius doubled, what change results in the amplitude of the voltage produced?

Accepted Answer

A)  It doubles. 
B)  It quadruples. 
C)  It is increased by a factor 23/2. 
D)  It stays the same. 
A)  It doubles. 
B)  It quadruples. 
C)  It is increased by a factor 23/2. 
D)  It stays the same.

Question 9

An AC voltage source, with a peak output of 120 V, results in dissipation of energy in a resistor at rate of 50.0 W. What is the value of the resistance?

Accepted Answer

A)  100 $\Omega$ 
B)  120$\Omega$ 
C)  144 $\Omega$ 
D)  72.0 $\Omega$ 
A)  100 $\Omega$ 
B)  120$\Omega$ 
C)  144 $\Omega$ 
D)  72.0 $\Omega$

Question 10

Transmitting power at high voltage, e.g., 400,000 V, reduces the power loss for transmission lines. But such a voltage would destroy electrical devices in household use. How then can such 400,000 V electricity be used in a normal house?

Accepted Answer

A)  The ground prongs on household plugs reduce the voltage to 120 V. 
B)  Before reaching households, transformers are used to reduce the voltage appropriately. 
C)  No matter the incoming voltage, a 120 V device only lets 120 V in. 
D)  The 400,000 V is just theoretical; long distance transmission lines actually use 120 V. 
A)  The ground prongs on household plugs reduce the voltage to 120 V. 
B)  Before reaching households, transformers are used to reduce the voltage appropriately. 
C)  No matter the incoming voltage, a 120 V device only lets 120 V in. 
D)  The 400,000 V is just theoretical; long distance transmission lines actually use 120 V.

Question 11

When an LCR series circuit is in resonance, its impedance is:

Accepted Answer

A)  "a maximum." 
B)  "equal to its resistance." 
C)  "zero." 
D)  " $\pi$2 $\Omega$." 
A)  "a maximum." 
B)  "equal to its resistance." 
C)  "zero." 
D)  " $\pi$2 $\Omega$."

Question 12

In the inductor of a 60-Hz AC series circuit, the peak voltage precedes the peak current in each cycle by what time interval?

Accepted Answer

A)  2.1 *10-3 s 
B)  8.3 *10-3 s 
C)  4.2 *10-3 s 
D)  1.7 *10-3 s 
A)  2.1 *10-3 s 
B)  8.3 *10-3 s 
C)  4.2 *10-3 s 
D)  1.7 *10-3 s

Question 13

In an AC circuit, the ratio of average current to maximum current is:

Accepted Answer

A)  zero. 
B)  0.707. 
C)  1.0. 
D)  0.5. 
A)  zero. 
B)  0.707. 
C)  1.0. 
D)  0.5.

Question 14

An AC series circuit has 8.00-$\Omega$ resistance, 15.00-$\Omega$ inductive reactance, and 10.00-$\Omega$ capacitive reactance. If an effective (rms) emf of 120 V is applied, what is the effective (rms) current value?

Accepted Answer

A)  26.0 A 
B)  5.31 A 
C)  9.23 A 
D)  12.7 A 
A)  26.0 A 
B)  5.31 A 
C)  9.23 A 
D)  12.7 A

Question 15

The peak voltage of an AC source is 400 V. What is the rms voltage?

Accepted Answer

A)  100 V 
B)  200 V 
C)  141 V 
D)  283 V 
A)  100 V 
B)  200 V 
C)  141 V 
D)  283 V

Question 16

What is the magnitude of the phase angle of an AC series circuit that is constructed of a 10.0-$\Omega$ resistor along with 20.00-$\Omega$ inductive reactance and 7.00-$\Omega$ capacitive reactance?

Accepted Answer

A)  18.4° 
B)  26.6° 
C)  52.4° 
D)  59.5° 
A)  18.4° 
B)  26.6° 
C)  52.4° 
D)  59.5°

Question 17

In an AC circuit operating at a frequency where the phase angle with respect to the current is 30°, what happens to the phase angle if the capacitance of the circuit is increased?

Accepted Answer

A)  It increases. 
B)  It decreases. 
C)  nothing 
D)  It decreases and can become zero. 
A)  It increases. 
B)  It decreases. 
C)  nothing 
D)  It decreases and can become zero.

Question 18

A transformer consists of a 1000-turn primary coil and a 4000-turn secondary coil. If the current in the secondary is 3.00 A, what is the primary current?

Accepted Answer

A)  6.00 A 
B)  0.750 A 
C)  48.0 A 
D)  12.0 A 
A)  6.00 A 
B)  0.750 A 
C)  48.0 A 
D)  12.0 A

Question 19

The output voltage of an AC generator is of the form   A typical frequency in household circuits is 60 Hz. Using radians for angular measure in this equation, what is the factor   in radians per second for this frequency?

Accepted Answer

A)  2 $\pi$ 
B)  120 
C)  377 
D)  60 
A)  2 $\pi$ 
B)  120 
C)  377 
D)  60

Question 20

In an LCR series circuit, if the AC frequency is increased to a very large value, what value does the magnitude of the angle between the current and voltage phasors approach?

Accepted Answer

A)  0° 
B)  45° 
C)  180° 
D)  90° 
A)  0° 
B)  45° 
C)  180° 
D)  90°

Exam 22: Alternating-Current Circuits and Machines

An electric motor produces 2.0 hp in a Vrms = 120 V circuit. Using 1 hp = 746 W, how long would it take this motor to do 1.0 kWh of work?

The rms current is equal to the direct current that:

An FM radio tuning circuit has a coil with an inductance of 0.0015 mH. What is the value of the capacitance if the set is tuned to 98 MHz?

A series LC circuit in a radio is in resonance with AM 1200 kHz. If the radio station is changed to AM 600 kHz, by what factor must the capacitance be multiplied to again achieve resonance?

Find the resonant frequency for a series LCR circuit where R = 20.0 Ω\OmegaΩ , C = 10.0 µF, and L = 8.0 mH.

An AM radio tuning circuit has a coil with an inductance of 4.00 mH and a capacitor set at 7.50 *10-6 μ\muμ F. What frequency will it detect?

A transformer is to be designed to increase the 30 kV (rms) output of a generator to the transmission line voltage of 345 kV (rms). If the primary winding has 60 turns, how many turns must the secondary have?

If the rotating coil used in a generator has its radius doubled, what change results in the amplitude of the voltage produced?

An AC voltage source, with a peak output of 120 V, results in dissipation of energy in a resistor at rate of 50.0 W. What is the value of the resistance?

Transmitting power at high voltage, e.g., 400,000 V, reduces the power loss for transmission lines. But such a voltage would destroy electrical devices in household use. How then can such 400,000 V electricity be used in a normal house?

When an LCR series circuit is in resonance, its impedance is:

In the inductor of a 60-Hz AC series circuit, the peak voltage precedes the peak current in each cycle by what time interval?

In an AC circuit, the ratio of average current to maximum current is:

An AC series circuit has 8.00- Ω\OmegaΩ resistance, 15.00- Ω\OmegaΩ inductive reactance, and 10.00- Ω\OmegaΩ capacitive reactance. If an effective (rms) emf of 120 V is applied, what is the effective (rms) current value?

The peak voltage of an AC source is 400 V. What is the rms voltage?

What is the magnitude of the phase angle of an AC series circuit that is constructed of a 10.0- Ω\OmegaΩ resistor along with 20.00- Ω\OmegaΩ inductive reactance and 7.00- Ω\OmegaΩ capacitive reactance?

In an AC circuit operating at a frequency where the phase angle with respect to the current is 30°, what happens to the phase angle if the capacitance of the circuit is increased?

A transformer consists of a 1000-turn primary coil and a 4000-turn secondary coil. If the current in the secondary is 3.00 A, what is the primary current?

The output voltage of an AC generator is of the form A typical frequency in household circuits is 60 Hz. Using radians for angular measure in this equation, what is the factor in radians per second for this frequency?

In an LCR series circuit, if the AC frequency is increased to a very large value, what value does the magnitude of the angle between the current and voltage phasors approach?

Introduction

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Forces and Motion in One Dimension

Forces and Motion in Two and Three Dimensions

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Temperature and Heat

Gases and Kinetic Theory

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Electric Potential

Electric Currents and Circuits

Magnetic Fields and Forces

Magnetic Induction

Electromagnetic Waves

Geometrical Optics

Wave Optics

Applications of Optics

Relativity

Quantum Theory

Atomic Theory

Nuclear Physics

Physics in the 21st Century

Filters

An electric motor produces 2.0 hp in a V_rms = 120 V circuit. Using 1 hp = 746 W, how long would it take this motor to do 1.0 kWh of work?

Find the resonant frequency for a series LCR circuit where R = 20.0 $\Omega$ , C = 10.0 µF, and L = 8.0 mH.

An AM radio tuning circuit has a coil with an inductance of 4.00 mH and a capacitor set at 7.50 *10^-⁶ $\mu$ F. What frequency will it detect?

An AC series circuit has 8.00- $\Omega$ resistance, 15.00- $\Omega$ inductive reactance, and 10.00- $\Omega$ capacitive reactance. If an effective (rms) emf of 120 V is applied, what is the effective (rms) current value?

What is the magnitude of the phase angle of an AC series circuit that is constructed of a 10.0- $\Omega$ resistor along with 20.00- $\Omega$ inductive reactance and 7.00- $\Omega$ capacitive reactance?