Question 1

An AM radio tuning circuit has a coil with an inductance of 1.65 mH and a capacitor set at 7.01 × 10−⁶ μF.What frequency will it detect? A) 1236 kHz B) 1480 kHz C) 2470 kHz D) 236 kHz E) 740 kHz

Accepted Answer

The resonant frequency of an LC circuit is given by the formula $ f = \frac{1}{2\pi\sqrt{LC}} $. Converting the given values to standard units, L = 1.65 mH = 1.65 × 10^-3 H and C = 7.01 × 10^-12 F. Plugging these into the formula gives approximately 1480 kHz.

Question 2

An FM radio tuning circuit has a coil with an inductance of 0.0021 mH.What is the value of the capacitance if the set is tuned to 102.7 MHz? A) 4.6 × 10−⁶ μF B) 3.6 × 10−⁶ μF C) 7.4 × 10−⁶ μF D) 1.14 × 10−⁶ μF E) 11.3 × 10−⁶ μF

Accepted Answer

The formula for capacitance in an FM radio tuning circuit is:

C = 1 / (2πf L)

Where:
C = capacitance in farads
f = frequency in hertz
L = inductance in henries
π = 3.1416

First, we need to convert the frequency to hertz:

102.7 MHz = 102.7 x 10^6 Hz

Now we can plug in the values and solve for capacitance:

C = 1 / (2π x 102.7 x 10^6 x 0.0021 x 10^-3)
C = 1.14 x 10^-16 F
C = 1.14 x 10^-7 µF
C = 0.114 µF

Therefore, the answer is D, 1.14 x 10^-7 µF.

Question 3

An ideal transformer is one that: A) has a turn ratio,N₂/N₁,equal to 1. B) works with direct current. C) experiences no power loss. D) has an output frequency of 60 Hz.

Accepted Answer

An ideal transformer is one that experiences no power loss, meaning that all the power input to the transformer is transferred to the output without any losses. Option A is incorrect because an ideal transformer can have a turn ratio different from 1:1. Options B and D are incorrect because an ideal transformer works only with alternating current (AC) and the output frequency depends on the input frequency and turn ratio.

Question 4

The primary winding of an electric train transformer has 235 turns,and the secondary has 72.If the input voltage is 191 V(rms),what is the output voltage?
A) 623 V
B) 18 V
C) 59 V
D) 345 V
E) ​191 V

Accepted Answer

We can use the transformer equation:

V1/V2 = N1/N2

where V1 is the input voltage (191 V), V2 is the output voltage (unknown), N1 is the number of turns in the primary winding (235), and N2 is the number of turns in the secondary winding (72).

Plugging in the values:

191/V2 = 235/72

Cross-multiplying:

72 x 191 = 235 x V2

Solving for V2:

V2 = (72 x 191) / 235

V2 ≈ 58.6 V

Therefore, the output voltage is approximately 59 V, which corresponds to choice C.

Question 5

A series RLC circuit in a radio is in resonance with AM 500 kHz.If the radio station is changed to AM 1500 kHz,by what factor must the capacitance be multiplied to again achieve resonance?
A) ​9
B) 3
C) 1
D) 1/3
E) ​1/9

Accepted Answer

The resonant frequency of an RLC circuit is inversely proportional to the square root of the capacitance. To triple the frequency from 500 kHz to 1500 kHz, the capacitance must be reduced by a factor of 9 (since frequency is proportional to the inverse square root of capacitance, (f ∝ 1/√C)).

Question 6

A transformer is to be designed to increase the 41-kV (rms)output of a generator to the transmission line voltage of 388 kV (rms).If the primary winding has 98 turns,how many turns must the secondary have?
A) 10
B) 8776
C) 927
D) 31
E) ​2852

Accepted Answer

The answer of A transformer is to be designed to...

Question 7

When an RLC series circuit is in resonance,its impedance is:
A) zero.
B) equal to its resistance.
C) a maximum.
D) π/2 Ω.

Accepted Answer

At resonance, the impedance of an RLC series circuit is purely resistive, meaning the inductive and capacitive reactances cancel each other out, leaving only the resistance as the impedance.

Question 8

Which one of the following scientists made the theoretical prediction that electromagnetic waves travel through a vacuum at the speed of light?
A) Hertz
B) Faraday
C) Maxwell
D) Lenz

Accepted Answer

James Clerk Maxwell made the theoretical prediction that electromagnetic waves travel through a vacuum at the speed of light in his famous set of equations known as "Maxwell's equations."

Question 9

What is the average power dissipation in an RLC series circuit in which R = 140 Ω,L = 0.38 H,and C = 10 µF driven at resonance by a 102-V (rms)source?
A) 70 W
B) 9 W
C) 15 W
D) 26 W
E) ​92 W

Accepted Answer

At resonance, the impedance of the circuit is purely resistive, so the average power dissipation is given by P = V^2/R, where V is the rms voltage. Thus, P = (102^2)/140 = 74.29 W, which rounds to 70 W.

Question 10

A transformer consists of a 705-turn primary coil and a 2757-turn secondary coil.If the current in the secondary is 1.11 A,what is the primary current?
A) 0.28 A
B) 2.20 A
C) 4.34 A
D) 1.11 A
E) ​0.56 A

Accepted Answer

According to the transformer equation, the ratio of the number of turns in the primary to the number of turns in the secondary is equal to the ratio of the primary current to the secondary current. Therefore,

705/2757 = Iprimary/1.11 A

Solving for Iprimary, we get:

Iprimary = (705/2757) x 1.11 A = 0.284 A ≈ 0.28 A (rounded to two significant figures)

Therefore, the correct answer is C, 4.34 A.

Question 11

An AC series circuit contains a resistor of 10 Ω,a capacitor of 1.20 μF and an inductor of 110 mH.What frequency should be used to create a resonance condition in the circuit?
A) 139 Hz
B) 1210 Hz
C) 1100 Hz
D) 438 Hz
E) ​877 Hz

Accepted Answer

Resonance occurs in an AC series circuit when the capacitive reactance (Xc) equals the inductive reactance (Xl):
Xc = 1/2πfC and Xl = 2πfL

At resonance: Xc = Xl
1/2πfC = 2πfL
f = 1 / 2π √(LC)

Substituting the given values: 
f = 1 / 2π √(110mH * 1.20μF)
f = 437.8 Hz ≈ 438 Hz

Therefore, the frequency that should be used to create a resonance condition in the circuit is 438 Hz, which is option D).

Question 12

A series RLC AC circuit is at resonance.It contains a resistor of 23 Ω,a capacitor of 0.25 μF and an inductor of 119 mH.If an effective (rms)voltage of 177 V is applied,what is the effective (rms)current when the circuit is in resonance?
A) 4.2 A
B) 7.7 A
C) 14 A
D) 2.6 A
E) ​28 A

Accepted Answer

At resonance, the impedance of the circuit is purely resistive and equals the resistance. Therefore, the effective (rms) current is calculated using Ohm's Law: I = V/R = 177 V / 23 Ω = 7.7 A.

Question 13

An AC power generator produces 60.64 A (rms)at 2195 V.The voltage is stepped up to 104,222 V by an ideal transformer,and the energy transmitted through a long-distance power line with a total resistance of 100 Ω.What is the rms current in the long-distance line?
A) 2879 A
B) 1.28 A
C) 60.64 A
D) 8.80 A
E) ​417.9 A

Accepted Answer

The power is conserved in an ideal transformer, so the power on the primary side (P_primary = V_primary * I_primary) equals the power on the secondary side (P_secondary = V_secondary * I_secondary). Solving for I_secondary gives I_secondary = (V_primary * I_primary) / V_secondary = (2195 V * 60.64 A) / 104,222 V = 1.28 A.

Question 14

Find the resonant frequency for a series RLC circuit where R = 21 Ω,C = 8.4 µF,and L = 2.80 mH.
A) 3260 Hz
B) 1038 Hz
C) 1470 kHz
D) 677 kHz
E) ​650 kHz

Accepted Answer

The resonant frequency for a series RLC circuit is given by the formula $ f_0 = \frac{1}{2\pi\sqrt{LC}} $. Substituting L = 2.80 mH and C = 8.4 µF into the formula gives $ f_0 \approx 1038 $ Hz.

Question 15

Which one of the following scientists first built and operated devices that could emit and detect man-made electromagnetic radiation?
A) Hertz
B) Ampere
C) Maxwell
D) Lenz

Accepted Answer

The answer of Which one of the following scientists first...

Question 16

An AC power generator produces 14 A (rms)at 2103 V.The energy is transmitted through a long-distance power line,which has a total resistance of 145 Ω.What percentage of the power delivered by the generator is dissipated as heat in the long-distance line if a step-up transformer is not used?
A) 3%
B) 19%
C) 31%
D) 97%
E) ​93%

Accepted Answer

The answer of An AC power generator produces 14 A...

Question 17

Which of the following combinations of circuit components can be used to make a tuner for a radio,to select the desired frequency?
A) fixed inductor,variable resistor
B) fixed resistor,variable inductor
C) fixed inductor,variable capacitor
D) fixed capacitor,variable resistor

Accepted Answer

A tuner for a radio is used to select the desired frequency from a range of frequencies. The combination of a fixed inductor and a variable capacitor is commonly used to create a resonant circuit that can be tuned to a specific frequency. The inductor and capacitor work together to create a high impedance at the resonant frequency, and a low impedance at other frequencies, which is how the tuner selects the desired frequency. The other options (A, B, and D) do not create resonant circuits that can be tuned to specific frequencies.

Question 18

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, causing them to cancel each other out and leaving only the resistive component in the circuit. This results in a peak in the amplitude of the current and voltage in the circuit.

Question 19

A series RLC circuit has a inductive reactance of 2 Ω and a capacitive reactance of 1/2 Ω.By what factor should the AC frequency be changed to put this circuit into resonance?
A) 2
B) 1/2
C) 1/1.41
D) 1.41
E) This circuit cannot be made to achieve resonance.

Accepted Answer

The answer of A series RLC circuit has a inductive...

Question 20

An AC series circuit contains a resistor of 16 Ω,an inductor of 43 mH and a variable capacitor.If the frequency of the applied voltage is 310 Hz,to what setting should the capacitor be set if resonance is achieved?
A) 60.5 µF
B) 24.5 µF
C) 11.9 µF
D) 6.1 µF
E) ​49.1 µF

Accepted Answer

The answer of An AC series circuit contains a resistor...

Quiz 21: Alternating-Current Circuits and Electromagnetic Waves

An AM radio tuning circuit has a coil with an inductance of 1.65 mH and a capacitor set at 7.01 × 10−⁶ μF.What frequency will it detect?

An FM radio tuning circuit has a coil with an inductance of 0.0021 mH.What is the value of the capacitance if the set is tuned to 102.7 MHz?

An ideal transformer is one that:

The primary winding of an electric train transformer has 235 turns,and the secondary has 72.If the input voltage is 191 V(rms) ,what is the output voltage?

A series RLC circuit in a radio is in resonance with AM 500 kHz.If the radio station is changed to AM 1500 kHz,by what factor must the capacitance be multiplied to again achieve resonance?

A transformer is to be designed to increase the 41-kV (rms) output of a generator to the transmission line voltage of 388 kV (rms) .If the primary winding has 98 turns,how many turns must the secondary have?

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

Which one of the following scientists made the theoretical prediction that electromagnetic waves travel through a vacuum at the speed of light?

What is the average power dissipation in an RLC series circuit in which R = 140 Ω,L = 0.38 H,and C = 10 µF driven at resonance by a 102-V (rms) source?

A transformer consists of a 705-turn primary coil and a 2757-turn secondary coil.If the current in the secondary is 1.11 A,what is the primary current?

An AC series circuit contains a resistor of 10 Ω,a capacitor of 1.20 μF and an inductor of 110 mH.What frequency should be used to create a resonance condition in the circuit?

A series RLC AC circuit is at resonance.It contains a resistor of 23 Ω,a capacitor of 0.25 μF and an inductor of 119 mH.If an effective (rms) voltage of 177 V is applied,what is the effective (rms) current when the circuit is in resonance?

An AC power generator produces 60.64 A (rms) at 2195 V.The voltage is stepped up to 104,222 V by an ideal transformer,and the energy transmitted through a long-distance power line with a total resistance of 100 Ω.What is the rms current in the long-distance line?

Find the resonant frequency for a series RLC circuit where R = 21 Ω,C = 8.4 µF,and L = 2.80 mH.

Which one of the following scientists first built and operated devices that could emit and detect man-made electromagnetic radiation?

An AC power generator produces 14 A (rms) at 2103 V.The energy is transmitted through a long-distance power line,which has a total resistance of 145 Ω.What percentage of the power delivered by the generator is dissipated as heat in the long-distance line if a step-up transformer is not used?

Which of the following combinations of circuit components can be used to make a tuner for a radio,to select the desired frequency?

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

A series RLC circuit has a inductive reactance of 2 Ω and a capacitive reactance of 1/2 Ω.By what factor should the AC frequency be changed to put this circuit into resonance?

An AC series circuit contains a resistor of 16 Ω,an inductor of 43 mH and a variable capacitor.If the frequency of the applied voltage is 310 Hz,to what setting should the capacitor be set if resonance is achieved?