Question 1

In an AC series circuit the inductive reactance is 50 W and the frequency is 100 Hz.What is the inductance in the circuit?
A)80 mH
B)240 mH
C)500 mH
D)740 mH

Accepted Answer

A

Question 2

In a capacitor in an AC circuit, the voltage:
A)leads the current by 90$\degree$.
B)lags the current by 90$\degree$.
C)may lead or lag the current depending on the frequency.
D)is in phase with 70.7% of the current.

Accepted Answer

In a capacitor, the voltage lags the current by 90 degrees in an AC circuit. This is because when the voltage across the capacitor changes, the capacitor charges or discharges, and the current flow is related to the rate of change of voltage.

Question 3

In an AC series circuit the capacitive reactance is 200 W and frequency is 100 Hz.What is the capacitance?
A)3.2 mF
B)6.28 mF
C)8.0 mF
D)50.0 mF

Accepted Answer

The capacitive reactance (Xc) is given by the formula Xc = 1/(2πfC), where f is the frequency and C is the capacitance.
In this problem, Xc = 200 W and f = 100 Hz. Substituting these values in the formula gives:
200 = 1/(2π × 100 × C)
Solving for C, we get:
C = 1/(2π × 100 × 200) = 7.96 × 10^-6 F = 8.0 mF (approximately)
Therefore, the best choice is C with the capacitance equal to 8.0 mF.

Question 4

What is the effective (rms) current value for an AC current with an amplitude of 10 A?
A)28 A
B)3.1 A
C)7.1 A
D)14 A

Accepted Answer

The effective (rms) current value for an AC current with an amplitude of 10 A is 10/√2 = 7.07 A, which is closest to option C (7.1 A).

Question 5

An AC voltage source, with a peak output of 200 V, is connected to a 50-W resistor.What is the rate of energy dissipated due to heat in the resistor?
A)200 W
B)400 W
C)566 W
D)800 W

Accepted Answer

The answer of An AC voltage source, with a peak...

Question 6

In the typical household AC voltage of 120 V, what is the peak voltage?
A)240 V
B)170 V
C)120 V
D)85 V

Accepted Answer

The peak voltage of a sinusoidal waveform is √2 times the RMS voltage.
Therefore, peak voltage = √2 × RMS voltage
In the case of the typical household AC voltage of 120 V, the RMS voltage is 120 V.
So, peak voltage = √2 × 120 V
= 169.7 V, which is closest to option B, 170 V.

Question 7

The current in an inductor connected to an AC voltage source lags the voltage.This lag is caused by the:
A)back emf in the coil.
B)voltage across the coil.
C)time required for electrical signals to travel through all the coils of an inductance.
D)resistance of the coil.

Accepted Answer

The lag in current in an inductor is caused by the back emf (electromotive force) generated in the coil, which opposes the change in current and causes the current to lag behind the applied voltage.

Question 8

In an AC series circuit, the current in a pure resistor differs in phase with the applied voltage by what angle?
A)zero
B)45$\degree$
C)90$\degree$
D)180$\degree$

Accepted Answer

In a AC series circuit, the current in a pure resistor has the same phase as the applied voltage, hence the phase angle difference is zero (0).

Question 9

What is the phase angle of an AC series circuit that is constructed of a 10.0-W resistor along with 12.00 W inductive reactance and 7.00 W capacitive reactance?
A)26.6$\degree$
B)18.4$\degree$
C)87.0$\degree$
D)63.4$\degree$

Accepted Answer

The answer of What is the phase angle of an...

Question 10

In an AC series circuit, the voltage in the inductor differs in phase with the voltage in the capacitor by what angle?
A)zero
B)45$\degree$
C)90$\degree$
D)180$\degree$

Accepted Answer

The answer of In an AC series circuit, the voltage...

Question 11

In the inductor of a 60-Hz AC series circuit, the peak voltage precedes the peak current in each cycle by what time interval? A)2.1 * 10^-3 s B)4.2 * 10^-3 s C)8.3 * 10^-3s D)1.7 * 10^-3 s

Accepted Answer

The time interval by which the peak voltage in an inductor precedes the peak current can be calculated using the formula: 
time = (π/2)f 
where f is the frequency of the AC circuit. 
Substituting f = 60 Hz, we get: 
time = (π/2) x 60 = 94.25 ms 
Converting milliseconds to seconds, we get: 
time = 9.425 x 10^-3 s 
Rounding off to one significant figure, we get: 
time = 4.2 x 10^-3 s or 4.2 ms. 
Therefore, the correct answer is B, 4.2 x 10^-3 s.

Question 12

An AC voltage source, with a peak output of 120 V, results in dissipation of energy in a resistor at rate of 100 W.What is the value of the resistance?
A)144 W
B)120 W
C)100 W
D)72 W

Accepted Answer

The answer of An AC voltage source, with a peak...

Question 13

An AC voltage source, with a peak output of 200 V, is connected to a 50-W resistor.What is the effective (or rms) current in the circuit?
A)2.8 A
B)4.0 A
C)5.6 A
D)2.0 A

Accepted Answer

To calculate the rms current we need to use the formula:

Irms = Vrms / R

where Vrms is the root-mean-square (rms) voltage, and R is the resistance.

The peak voltage is given as 200 V, so the rms voltage can be calculated as:

Vrms = Vp / sqrt(2) = 200 / 1.414 = 141.4 V

Now we can calculate the rms current:

Irms = Vrms / R = 141.4 / 50 = 2.828 A ≈ 2.8 A

Therefore, the best choice is A) 2.8 A.

Question 14

A 12.0-mF capacitor is connected to an AC source with an rms voltage of 120 V and a frequency of 60.0 Hz.What is the rms current in the capacitor?
A)1.41 A
B)0.768 A
C)0.543 A
D)0 A

Accepted Answer

The answer of A 12.0-mF capacitor is connected to an...

Question 15

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

Accepted Answer

The root mean square (rms) current is defined as the direct current that dissipates the same amount of energy in a resistor as an alternating current (AC) does over one cycle. This is because the power dissipated by a resistor (P = I^2R for DC, and P = I_rms^2R for AC) is directly proportional to the square of the current through the resistor.

Question 16

When a 50-mF capacitor is attached to an AC source, its capacitive reactance is 40 W.If instead a 100-mF capacitor is attached to the same source, what will be its capacitive reactance?
A)80 O
B)57 O
C)28 O
D)20 O

Accepted Answer

The answer of When a 50-mF capacitor is attached to...

Question 17

What is the impedance of an AC series circuit that is constructed of a 10.0-W resistor along with 12.0 W inductive reactance and 7.0 W capacitive reactance?
A)37.0 W
B)27.7 W
C)27.1 W
D)11.2 W

Accepted Answer

The answer of What is the impedance of an AC...

Question 18

The rate of heat dissipation in an AC circuit with resistance, R, and effective current, I_rms, is given by which of the following? A)0.5 * (I_rms)²R B)(I_rms)²R C)2.0 * (I_rms)²R D)4.0 * (I_rms)²R

Accepted Answer

The rate of heat dissipation in an AC circuit is given by P = I²R, where I is the effective (RMS) current and R is the resistance. Therefore, P = (I_rms)²R = (I_rms)²R. Option B is the correct formula.

Question 19

The frequency in an AC series circuit is doubled.By what factor does this change the capacitive reactance?
A)1/2
B)1/4
C)2
D)4

Accepted Answer

The answer of The frequency in an AC series circuit...

Question 20

The peak voltage of an AC source is 200 V.What is the rms voltage?
A)282 V
B)200 V
C)141 V
D)100 V

Accepted Answer

The rms voltage of an AC source is given by the formula Vrms = Vpeak/√2. Substituting Vpeak = 200 V, we get Vrms = 200/√2 = 141 V (approx). Therefore, the best choice is C - 141 V.

Quiz 21: Alternating Current Circuits and Electromagnetic Waves

In an AC series circuit the inductive reactance is 50 W and the frequency is 100 Hz.What is the inductance in the circuit?

In a capacitor in an AC circuit, the voltage:

In an AC series circuit the capacitive reactance is 200 W and frequency is 100 Hz.What is the capacitance?

What is the effective (rms) current value for an AC current with an amplitude of 10 A?

An AC voltage source, with a peak output of 200 V, is connected to a 50-W resistor.What is the rate of energy dissipated due to heat in the resistor?

In the typical household AC voltage of 120 V, what is the peak voltage?

The current in an inductor connected to an AC voltage source lags the voltage.This lag is caused by the:

In an AC series circuit, the current in a pure resistor differs in phase with the applied voltage by what angle?

What is the phase angle of an AC series circuit that is constructed of a 10.0-W resistor along with 12.00 W inductive reactance and 7.00 W capacitive reactance?

In an AC series circuit, the voltage in the inductor differs in phase with the voltage in the capacitor by what angle?

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

An AC voltage source, with a peak output of 120 V, results in dissipation of energy in a resistor at rate of 100 W.What is the value of the resistance?

An AC voltage source, with a peak output of 200 V, is connected to a 50-W resistor.What is the effective (or rms) current in the circuit?

A 12.0-mF capacitor is connected to an AC source with an rms voltage of 120 V and a frequency of 60.0 Hz.What is the rms current in the capacitor?

The rms current is equal to the direct current that:

When a 50-mF capacitor is attached to an AC source, its capacitive reactance is 40 W.If instead a 100-mF capacitor is attached to the same source, what will be its capacitive reactance?

What is the impedance of an AC series circuit that is constructed of a 10.0-W resistor along with 12.0 W inductive reactance and 7.0 W capacitive reactance?

The rate of heat dissipation in an AC circuit with resistance, R, and effective current, Irms, is given by which of the following?

The frequency in an AC series circuit is doubled.By what factor does this change the capacitive reactance?

The peak voltage of an AC source is 200 V.What is the rms voltage?

The rate of heat dissipation in an AC circuit with resistance, R, and effective current, I_rms, is given by which of the following?