Question 1

An AC series circuit has 12.0 W resistance,15.00 W inductive reactance and 10.00 W capacitive reactance.If an effective (rms)emf of 120 V is applied,what is the effective (rms)current value?
A)5.31 A
B)9.23 A
C)10.8 A
D)26.0 A

Accepted Answer

The answer of An AC series circuit has 12.0 W...

Question 2

In an RLC series circuit the capacitive reactance is 24 W.If the AC frequency doubles,what will be the resulting capacitive reactance?
A)24 W
B)12 W
C)48 W
D)Additional information is need to find the value.

Accepted Answer

Capacitive reactance (Xc) is inversely proportional to the frequency (f), so if the frequency doubles, the capacitive reactance will be halved.

Question 3

The power dissipated in an AC series circuit increases as the phase angle approaches what value?
A)zero
B)45 $\degree$
C)90 $\degree$
D)180 $\degree$

Accepted Answer

The power dissipated in an AC circuit is maximized when the phase angle between the voltage and current is zero, as this indicates that they are in phase and the power factor is 1.

Question 4

A resistor,inductor and capacitor are connected in series,each with effective (rms)voltage of 65 V,140 V and 80 V,respectively.If the resistor is rated at 24 W,what is the average power dissipated in the circuit?
A)88 W
B)176 W
C)238 W
D)323 W

Accepted Answer

Using the formula for impedance in a series circuit:
Z = sqrt(R^2 + (XL - XC)^2)
where R is the resistance, XL is the inductive reactance, and XC is the capacitive reactance.

Given:
Effective voltage (rms) of resistor, V_R = 65 V
Effective voltage (rms) of inductor, V_L = 140 V
Effective voltage (rms) of capacitor, V_C = 80 V
Resistance, R = 24 ohms

We can first find the values of XL and XC using the formulas:
XL = 2πfL
where f is the frequency and L is the inductance
XC = 1/(2πfC)
where f is the frequency and C is the capacitance

Assuming a frequency of 50 Hz (standard AC frequency), we get:
XL = 2π(50)(L) = 140 ohms
XC = 1/(2π(50)(C)) = 31.8 ohms

We can then find the total impedance of the circuit:
Z = sqrt(R^2 + (XL - XC)^2) = 134.5 ohms

The total current in the circuit is given by:
I = V/Z = (65 + 140 + 80)/134.5 = 2.30 A (rms)

The average power dissipated in the circuit is given by:
P = I^2R = (2.30)^2(24) = 126.7 W

However, this only accounts for the power dissipated in the resistor. The inductor and capacitor have reactive power, which means they store and release energy without dissipating it. Therefore, we need to also consider the reactive power in the circuit.

The reactive power in the inductor is given by:
Q_L = V_L^2/XL = 140^2/140 = 140 W

The reactive power in the capacitor is given by:
Q_C = V_C^2/XC = 80^2/31.8 = 202 W

The total reactive power in the circuit is given by:
Q = Q_L - Q_C = -62 W

The negative sign indicates that the circuit is capacitive, meaning the capacitor is absorbing reactive power while the inductor is releasing it.

The total apparent power in the circuit is given by:
S = VI = (65 + 140 + 80)(2.30) = 654 VA

The total power factor of the circuit is given by:
pf = P/S = 126.7/654 = 0.193

The average power dissipated in the circuit is then given by:
P_avg = S(pf) = 654(0.193) = 126.3 W

Since the resistor is the only component dissipating real power, the average power dissipated in the circuit is approximately equal to the power dissipated in the resistor, which is 126.7 W. The closest answer choice is 176 W, which is option B.

Question 5

What is the average power dissipation in a series RC circuit if R = 5.00 kW,C = 2.00 µF,and V = (170 V)cos 300t?
A)2.60 W
B)2.74 W
C)28.2 W
D)157 W

Accepted Answer

The average power dissipation in a series RC circuit is given by P_avg = (V_rms^2) / R, where V_rms = V_peak / √2. Here, V_peak = 170 V, so V_rms = 170 / √2. Substituting the values, P_avg = (170/√2)^2 / 5000 = 2.60 W.

Question 6

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

Accepted Answer

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

Question 7

In an RLC series circuit the phase angle between the current and voltages is 30 $\degree$.If the AC frequency doubles,what is the resulting phase angle?
A)30 $\degree$
B)more than 30 $\degree$
C)less than 30 $\degree$
D)Additional information is needed to reach a determination.

Accepted Answer

The phase angle in an RLC series circuit is given by arctan((XL-XC)/R), where XL and XC are the reactance of inductor and capacitor respectively. As the AC frequency doubles, the reactances of the inductor and capacitor also double. Therefore, the numerator of the phase angle equation increases, which means that the phase angle will increase. Hence, the resulting phase angle will be more than 30 degrees. Therefore, the correct answer is B.

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)3.0
D)Information is insufficient to determine answer.

Accepted Answer

The impedance of an AC circuit depends on the resistance, inductive reactance, and capacitive reactance. Tripling the frequency will affect the inductive and capacitive reactances differently, and without specific values for these components, the overall change in impedance cannot be determined.

Question 9

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 $\degree$
B)0 $\degree$
C)-90 $\degree$
D)45 $\degree$

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 degrees.

Question 10

Resonance occurs in an AC series circuit when which of the following conditions is met?
A)resistance equals capacitive reactance
B)resistance equals inductive reactance
C)capacitive reactance equals inductive reactance
D)capacitive reactance equals zero

Accepted Answer

Resonance occurs when the capacitive reactance and inductive reactance are equal in magnitude and opposite in sign, leading to a cancellation of the reactive components and a high impedance at the resonant frequency.

Question 11

Consider an AC series circuit containing a coil,capacitor and resistance.Tripling the frequency will change the capacitive reactance by what factor?
A)1/3
B)1.0
C)1.73
D)3.0

Accepted Answer

Capacitive reactance (Xc) is inversely proportional to frequency (f). Thus, tripling the frequency will result in 1/3 of the original capacitive reactance.

Question 12

The power factor in an AC series circuit is equal to which of the following ratios?
A)resistance to inductive reactance
B)capacitive reactance to inductive reactance
C)inductive reactance to capacitive reactance
D)resistance to impedance

Accepted Answer

The power factor in an AC series circuit is equal to the ratio of resistance to impedance. This is because the power factor is a measure of how much of the apparent power is actually converted into real power, and the resistance represents the real power while the impedance represents the apparent power.

Question 13

A resistor,inductor,and capacitor are connected in series,each with an effective (rms)voltage of 65 V,140 V,and 80 V,respectively.What is the magnitude of the phase angle in this circuit?
A)22 $\degree$
B)28 $\degree$
C)37 $\degree$
D)43 $\degree$

Accepted Answer

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

Question 14

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 50 V and 75 V (rms),respectively.What is the effective (rms)voltage of the source?
A)25 V
B)63 V
C)90 V
D)125 V

Accepted Answer

In a series circuit, the voltage drops across each component add up to the total voltage of the source. 
So, Vsource = Vresistor + Vcapacitor 
RMS voltage of resistor = 50 V 
RMS voltage of capacitor = 75 V 
Thus, Vsource = 50 V + 75 V = 125 V (rms) 
Therefore, the correct choice is option (D) 125 V.

Question 15

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 16

A resistor,inductor,and capacitor are connected in series,each with effective (rms)voltage of 65 V,140 V,and 80 V,respectively.What is the value of the effective (rms)voltage of the applied source in the circuit?
A)48 V
B)88 V
C)95 V
D)285 V

Accepted Answer

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

Question 17

An AC series circuit has 12.0 W resistance,15.00 W inductive reactance and 10.00 W capacitive reactance.If an effective (rms)emf of 120 V is applied,what is the power output?
A)1 540 W
B)1 300 W
C)1 160 W
D)1 020 W

Accepted Answer

The answer of An AC series circuit has 12.0 W...

Question 18

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 $\degree$
B)0 $\degree$
C)-90 $\degree$
D)45 $\degree$

Accepted Answer

In an RLC series circuit, if the AC frequency is decreased to a very small value, the reactance of the inductor will become very large, while the reactance of the capacitor will become very small. This means that the circuit will behave as a purely inductive circuit. In a purely inductive circuit, the current lags behind the voltage by 90 degrees. Therefore, the phase angle between the current and voltage will approach -90 degrees, which is given as choice C.

Question 19

A 200-W resistor is connected in series with a 10-µF capacitor and a 60-Hz,120-V (rms)line voltage.If electrical energy costs 5.0¢ per kWh,how much does it cost to leave this circuit connected for 24 hours?
A)62¢
B)31¢
C)5.2¢
D)3.1¢

Accepted Answer

The answer of A 200-W resistor is connected in series...

Question 20

Consider an AC series circuit containing a coil,capacitor and resistance.Tripling the frequency will change the inductive reactance by what factor?
A)1/3
B)1.0
C)1.73
D)3.0

Accepted Answer

Inductive reactance (XL) is directly proportional to the frequency (f) of the AC circuit. Therefore, tripling the frequency will triple the inductive reactance.

Quiz 21: Alternating Current Circuits and Electromagnetic Waves

An AC series circuit has 12.0 W resistance,15.00 W inductive reactance and 10.00 W capacitive reactance.If an effective (rms) emf of 120 V is applied,what is the effective (rms) current value?

In an RLC series circuit the capacitive reactance is 24 W.If the AC frequency doubles,what will be the resulting capacitive reactance?

The power dissipated in an AC series circuit increases as the phase angle approaches what value?

A resistor,inductor and capacitor are connected in series,each with effective (rms) voltage of 65 V,140 V and 80 V,respectively.If the resistor is rated at 24 W,what is the average power dissipated in the circuit?

What is the average power dissipation in a series RC circuit if R = 5.00 kW,C = 2.00 µF,and V = (170 V) cos 300t?

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

In an RLC series circuit the phase angle between the current and voltages is 30 $\degree$ .If the AC frequency doubles,what is the resulting phase angle?

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

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?

Resonance occurs in an AC series circuit when which of the following conditions is met?

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

The power factor in an AC series circuit is equal to which of the following ratios?

A resistor,inductor,and capacitor are connected in series,each with an effective (rms) voltage of 65 V,140 V,and 80 V,respectively.What is the magnitude of the phase angle in this circuit?

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 50 V and 75 V (rms) ,respectively.What is the effective (rms) voltage of the source?

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

A resistor,inductor,and capacitor are connected in series,each with effective (rms) voltage of 65 V,140 V,and 80 V,respectively.What is the value of the effective (rms) voltage of the applied source in the circuit?

An AC series circuit has 12.0 W resistance,15.00 W inductive reactance and 10.00 W capacitive reactance.If an effective (rms) emf of 120 V is applied,what is the power output?

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 200-W resistor is connected in series with a 10-µF capacitor and a 60-Hz,120-V (rms) line voltage.If electrical energy costs 5.0¢ per kWh,how much does it cost to leave this circuit connected for 24 hours?

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