Question 1

In an RL circuit,which of the following is a possible magnitude of a phase angle? A)45^° B)315^° C)225^° D)135^°

Accepted Answer

In an RL circuit, the phase angle is typically between 0° and 90° because the current lags the voltage. 45° is within this range.

Question 2

In an RLC series circuit the capacitive reactance is 19.5 Ω.If the AC frequency triples,what will be the resulting capacitive reactance?
A)11.3 Ω
B)6.5 Ω
C)33.8 Ω
D)58.5 Ω
E)Additional information is need to find the value.

Accepted Answer

The capacitive reactance (Xc) is inversely proportional to the frequency (f), given by the formula Xc = 1/(2πfC), where C is the capacitance. If the frequency triples, the new capacitive reactance will be one-third of the original, so 19.5 Ω / 3 = 6.5 Ω.

Question 3

A resistor,inductor,and capacitor are connected in series,each with effective (rms)voltage of 64.0 V,87.6 V,and 69.0 V,respectively.What is the value of the effective (rms)voltage of the applied source in the circuit?
A)82.6 V
B)66.6 V
C)83.7 V
D)220.6 V
E)129 V

Accepted Answer

The answer of A resistor,inductor,and capacitor are connected in series,each...

Question 4

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°
C)90°
D)180°

Accepted Answer

In an AC series circuit, the voltage across the inductor leads the current by 90°, while the voltage across the capacitor lags the current by 90°. This results in a phase difference of 180° between the voltage in the inductor and the voltage in the capacitor.

Question 5

A resistor and capacitor are connected in series with an applied AC voltage source.Separate voltmeter readings across the resistor and capacitor give values of 23 V and 29 V (rms),respectively.What is the effective (rms)voltage of the source?
A)7.2 V
B)47 V
C)37 V
D)26 V
E)18 V

Accepted Answer

We know that the voltage across a resistor (Vr) and a capacitor (Vc) in series with an AC voltage source are given by:

Vr = IR × R          and         Vc = IC × XC

where IR and IC are the currents flowing through the resistor and capacitor, and R and XC are the resistance and reactance of the resistor and capacitor respectively.

Since the resistor and capacitor are in series, the current flowing through them must be the same. Hence, we can write:

IR = IC = I        (let's call it I)

We also know that the voltage across the source (Vs) is the phasor sum of the voltage across the resistor and the voltage across the capacitor, i.e.,

Vs = √(Vr^2 + Vc^2)

Substituting the given values, we get:

Vs = √(23^2 + 29^2) = √(529 + 841) = √1370 = 37.01 V (approx.)

Therefore, the effective (rms) voltage of the source is 37 V.

Question 6

An AC circuit consists of a 60-Hz source,a 200-Ω resistor,and a 1.06-H inductor,all in series.What is the impedance of this circuit?
A)400 Ω
B)280 Ω
C)600 Ω
D)450 Ω

Accepted Answer

The answer of An AC circuit consists of a 60-Hz...

Question 7

In an RLC series circuit,if the AC frequency is decreased to a very small value,what value does the phase angle between the current and voltage approach?
A)90°
B)0°
C)-90°
D)45°

Accepted Answer

At very small values of AC frequency, the impedance of the inductor becomes very high while the impedance of the capacitor becomes very low. Hence, the circuit becomes predominantly capacitive. In a purely capacitive circuit, the phase angle between the voltage and current is -90°. Therefore, as the AC frequency decreases, the phase angle between the current and voltage in a RLC series circuit approaches -90° (or 270°).

Question 8

Consider an AC series circuit containing a coil,capacitor and resistance.Tripling the frequency will change the circuit's impedance by what factor?
A)1/3
B)1.0
C)3
D)Information is insufficient to determine answer.

Accepted Answer

The impedance of an AC series circuit containing a coil, capacitor, and resistor depends on the frequency, but without specific values for the resistance, inductance, and capacitance, it's impossible to determine how tripling the frequency will affect the overall impedance.

Question 9

A series circuit has equal values for resistance,capacitive reactance,and inductive reactance.The phase angle for this circuit is:
A)60°.
B)-60°.
C)180°.
D)not given.

Accepted Answer

The answer of A series circuit has equal values for...

Question 10

In an RLC circuit,the maximum current is 1 amp.What is the average current?
A)  A
B)  A
C)(1/2)A
D)None of the above.

Accepted Answer

The answer of In an RLC circuit,the maximum current is...

Question 11

What is the impedance of an AC series circuit that is constructed of a 10.0-Ω resistor along with 24.0-Ω inductive reactance and 7.0-Ω capacitive reactance?
A)19.7 Ω
B)11.2 Ω
C)41.0 Ω
D)27.7 Ω

Accepted Answer

To calculate the total impedance (Z) of the circuit, we need to add the resistive, inductive, and capacitive impedances vectorially. Mathematically,

Z^2 = R^2 + (XL - XC)^2

Where R is the resistance, XL is the inductive reactance, and XC is the capacitive reactance.

Substituting the given values, we get:

Z^2 = (10)^2 + (24 - 7)^2

Z^2 = 10^2 + 17^2

Z^2 = 10^2 + 289

Z^2 = 389

Z = sqrt(389)

Z = 19.7 Ω

Therefore, the impedance of the AC series circuit is 19.7 Ω, which is closest to option A (19.7 Ω).

Question 12

In an RLC series circuit,if the AC frequency is increased to a very large value,what value does the phase angle between the current and voltage approach?
A)90°
B)0°
C)-90°
D)45°

Accepted Answer

At very high frequencies, the inductive reactance becomes much larger than the capacitive reactance, causing the circuit to behave like a purely inductive circuit where the phase angle approaches 90°.

Question 13

An AC series circuit has 16.5 Ω resistance,12.8 Ω inductive reactance and 8.27 Ω capacitive reactance.If an effective (rms)emf of 145 V is applied,what is the effective (rms)current value?
A)7.56 A
B)8.47 A
C)0.495 A
D)23.7 A
E)6.89 A

Accepted Answer

The answer of An AC series circuit has 16.5 Ω...

Question 14

What is the phase angle of an AC series circuit that is constructed of a 14.5-Ω resistor along with 16.5-Ω inductive reactance and 9.41-Ω capacitive reactance?
A)26.1°
B)11.9°
C)43.1°
D)35.0°
E)38.7°

Accepted Answer

The phase angle ($\theta$) in an AC circuit can be calculated using the formula $\theta = \tan^{-1}\left(\frac{X_L - X_C}{R}\right)$, where $X_L$ is the inductive reactance, $X_C$ is the capacitive reactance, and $R$ is the resistance. Plugging in the given values: $\theta = \tan^{-1}\left(\frac{16.5 - 9.41}{14.5}\right) = \tan^{-1}(0.489)$, which gives a phase angle of approximately 26.1°.

Question 15

Consider an AC series circuit containing a coil,capacitor and resistance.Doubling the frequency will change the inductive reactance by what factor?
A)1/2
B)1
C) 
D)2
E)1/2.

Accepted Answer

The answer of Consider an AC series circuit containing a...

Question 16

Consider an AC series circuit containing a coil,capacitor,and resistance.Doubling the frequency will change the capacitive reactance by what factor? A)1/2 B)1 C) D)2 E)2²

Accepted Answer

The capacitive reactance, XC, is inversely proportional to frequency, f, and is given by XC=1/(2πfC). Doubling the frequency will result in XC=1/(2π(2f)C), which simplifies to XC=1/(4πfC). Thus, the capacitive reactance will be halved, resulting in a factor of 1/2.

Question 17

In an AC circuit,the ratio of average current to maximum current is:
A)zero.
B)0.5.
C)0.707.
D)1.0.

Accepted Answer

The answer of In an AC circuit,the ratio of average...

Question 18

An RLC circuit is connected across an AC power source.How are the maximum and rms voltages from the power source related? A)ΔV_max= ΔV_rms B)ΔV_max = ΔV_rms/ C)ΔV_max= 2ΔV_rms D)ΔVmax = ΔVrms/2

Accepted Answer

The answer of An RLC circuit is connected across an...

Question 19

A 400-Ω resistor and an inductor are connected in parallel across a 300-Hz source.If the amplitude of the current in the resistor is equal to that in the inductor,what is the value of the inductance? A)0.212 H B)0.666 H C)1.33 × 10^-6 H D)0.333 H

Accepted Answer

The amplitude of the current in the resistor is equal to that in the inductor, which means the resistive reactance (R) equals the inductive reactance (XL). XL = 2πfL, where f is the frequency and L is the inductance. Given R = 400 Ω and f = 300 Hz, we solve for L: L = R / (2πf) = 400 / (2π*300) ≈ 0.212 H.

Question 20

What is the impedance of an AC series circuit that is constructed of a 12.5-Ω resistor along with 13.6-Ω inductive reactance and 3.43-Ω capacitive reactance?
A)29.5 Ω
B)22.7 Ω
C)18.2 Ω
D)16.1 Ω
E)3.36 Ω

Accepted Answer

The impedance of an AC series circuit is calculated using the formula Z = √(R² + (X_L - X_C)²), where R is the resistance, X_L is the inductive reactance, and X_C is the capacitive reactance. Substituting the given values: Z = √(12.5² + (13.6 - 3.43)²) = √(12.5² + 10.17²) = √(156.25 + 103.4289) = √259.6789 ≈ 16.1 Ω.

Quiz 21: Alternating-Current Circuits and Electromagnetic Waves

In an RL circuit,which of the following is a possible magnitude of a phase angle?

In an RLC series circuit the capacitive reactance is 19.5 Ω.If the AC frequency triples,what will be the resulting capacitive reactance?

A resistor,inductor,and capacitor are connected in series,each with effective (rms) voltage of 64.0 V,87.6 V,and 69.0 V,respectively.What is the value of the effective (rms) voltage of the applied source in the circuit?

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

A resistor and capacitor are connected in series with an applied AC voltage source.Separate voltmeter readings across the resistor and capacitor give values of 23 V and 29 V (rms) ,respectively.What is the effective (rms) voltage of the source?

An AC circuit consists of a 60-Hz source,a 200-Ω resistor,and a 1.06-H inductor,all in series.What is the impedance of this circuit?

In an RLC series circuit,if the AC frequency is decreased to a very small value,what value does the phase angle between the current and voltage approach?

Consider an AC series circuit containing a coil,capacitor and resistance.Tripling the frequency will change the circuit's impedance by what factor?

A series circuit has equal values for resistance,capacitive reactance,and inductive reactance.The phase angle for this circuit is:

In an RLC circuit,the maximum current is 1 amp.What is the average current?

What is the impedance of an AC series circuit that is constructed of a 10.0-Ω resistor along with 24.0-Ω inductive reactance and 7.0-Ω capacitive reactance?

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

An AC series circuit has 16.5 Ω resistance,12.8 Ω inductive reactance and 8.27 Ω capacitive reactance.If an effective (rms) emf of 145 V is applied,what is the effective (rms) current value?

What is the phase angle of an AC series circuit that is constructed of a 14.5-Ω resistor along with 16.5-Ω inductive reactance and 9.41-Ω capacitive reactance?

Consider an AC series circuit containing a coil,capacitor and resistance.Doubling the frequency will change the inductive reactance by what factor?

Consider an AC series circuit containing a coil,capacitor,and resistance.Doubling the frequency will change the capacitive reactance by what factor?

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

An RLC circuit is connected across an AC power source.How are the maximum and rms voltages from the power source related?

A 400-Ω resistor and an inductor are connected in parallel across a 300-Hz source.If the amplitude of the current in the resistor is equal to that in the inductor,what is the value of the inductance?

What is the impedance of an AC series circuit that is constructed of a 12.5-Ω resistor along with 13.6-Ω inductive reactance and 3.43-Ω capacitive reactance?