Question 1

An AM radio tuning circuit has a coil with an inductance of 6.00 mH and a capacitor set at 7.50 * 10^-6 mF.What frequency will it detect? A)550 kHz B)750 kHz C)1 060 kHz D)1 520 kHz

Accepted Answer

The answer of An AM radio tuning circuit has a...

Question 2

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

Accepted Answer

The answer of When an RLC series circuit is in...

Question 3

The primary winding of an electric train transformer has 400 turns, and the secondary has 50.If the input voltage is 120 V(rms), what is the output voltage?
A)480 V
B)60 V
C)15 V
D)10 V

Accepted Answer

The answer of The primary winding of an electric train...

Question 4

An AC power generator produces 25 A (rms) at 3 600 V.The energy is transmitted through a long-distance power line, which has a total resistance of 100 W.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)0.09%
B)1.8%
C)32%
D)69%

Accepted Answer

The power delivered by the generator can be calculated using the formula P = VI, where V is the voltage and I is the current. Therefore, P = (3600V)(25A) = 90,000W.

The power dissipated as heat in the long-distance line can be calculated using the formula P = I^2R, where R is the resistance of the line. Therefore, P = (25A)^2(100Ω) = 62,500W.

The percentage of power dissipated as heat in the line can be calculated as (power dissipated/power delivered)*100%. Thus, the percentage is (62,500W/90,000W)*100% = 69.4%, which rounds to 69%. Therefore, the answer is D, 69%.

Question 5

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 80 turns, how many turns must the secondary have?
A)6
B)70
C)920
D)9 200

Accepted Answer

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

Question 6

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 is used to select the desired frequency in a radio. This can be achieved by using a circuit that can resonate at the desired frequency. A resonant circuit typically consists of an inductor and capacitor in parallel or series. By changing the value of the capacitor, the resonant frequency of the circuit can be changed. Therefore, choice C (fixed inductor, variable capacitor) is the best combination to make a tuner for a radio.

Question 7

A series RLC circuit in a radio is in resonance with AM 600 kHz.If the radio station is changed to AM 1 200 kHz, by what factor must the capacitance be multiplied to again achieve resonance?
A)4
B)2
C)1/2
D)1/4

Accepted Answer

Resonant frequency of an series RLC circuit is given as 
fr = 1/(2*pi*sqrt(LC))
As the radio station changes to 1200kHz, the resonant frequency of the circuit changes to fr'. Let's solve for fr' and equate it to 1200kHz.
1200*10^3 = 1/(2*pi*sqrt(L*(C' factor)))
Now, we need to find the factor by which capacitance (C) must be multiplied to achieve resonance again. From the above equation, resonant frequency (fr') is inversely proportional to sqrt(C'), i.e, when C is multiplied by a factor of 'n', fr' is multiplied by a factor of '1/n'. Let's put that in the equation and simplify it.

1200*10^3 = 1/(2*pi*sqrt(L*n^2*C))

n^2 = C'/C = 1200^2/600^2

n = 1/2

Therefore, C must be multiplied by a factor of 1/2 to achieve resonance again.

Question 8

An FM radio tuning circuit has a coil with an inductance of 0.003 0 mH.What is the value of the capacitance if the set is tuned to 98 MHz? A)1.8 * 10^-6 mF B)12 * 10^-6 mF C)0.98 * 10^-6 mF D)0.88 * 10^-6 mF

Accepted Answer

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

C = 1 / (4π²f²L)

where C is the capacitance in farads, L is the inductance in henries, and f is the frequency in hertz.

Substituting the given values, we get:

C = 1 / (4π² x 98² x 0.003 x 10^-3) = 0.88 x 10^-6 F = 0.88 μF

Therefore, the correct answer is D: 0.88 * 10^-6 mF.

Question 9

An AC power generator produces 50 A (rms) at 3 600 V. The voltage is stepped up to 100 000 V by an ideal transformer, and the energy transmitted through a long-distance power line with a total resistance of 100 W.What is the rms current in the long-distance line?
A)1.0 A
B)1.8 A
C)24 A
D)1 000 A

Accepted Answer

To solve this problem, we use the formula:

I2 = (V1/V2) * I1

Where I1 and V1 are the current and voltage of the generator, I2 and V2 are the current and voltage in the long-distance line.

Therefore:

I2 = (3,600 V / 100,000 V) * 50 A = 1.8 A

Next, we use Ohm's Law to calculate the voltage drop across the power line:

V = I * R = 1.8 A * 100 W = 180 V

Finally, we use the Pythagorean theorem to find the rms current in the long-distance line:

Irms = sqrt(I2^2 + (V/R)^2) = sqrt((1.8 A)^2 + (180 V / 100 W)^2) = rms current is approximately 1.8 A.

Question 10

A transformer consists of a 500-turn primary coil and a 2 000-turn secondary coil.If the current in the secondary is 3.00 A, what is the primary current?
A)0.750 A
B)1.33 A
C)12.0 A
D)48.0 A

Accepted Answer

The answer of A transformer consists of a 500-turn primary...

Question 11

Find the resonant frequency for a series RLC circuit where R = 20.0 W, C = 10.0 µF, and L = 4.0 mH.
A)507 Hz
B)796 Hz
C)1.59 kHz
D)5.00 kHz

Accepted Answer

The answer of Find the resonant frequency for a series...

Question 12

An AC series circuit contains a resistor of 20 W, an inductor of 30 mH and a variable capacitor.If the frequency of the applied voltage is 500 Hz, to what setting should the capacitor be set if resonance is achieved?
A)0.8 µF
B)1.6 µF
C)2.4 µF
D)3.4 µF

Accepted Answer

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

Question 13

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 experiences no power loss, which means that the input power is equal to the output power. Choices A and D are not correct because the turn ratio and output frequency do not determine whether a transformer is ideal. Choice B is not correct because transformers only work with alternating current.

Question 14

What is the average power dissipation in an RLC series circuit in which R = 100 W, L = 0.1 H, and C = 10 µF driven at resonance by a 100-V (rms) source?
A)100 W
B)500 W
C)1 000 W
D)2 W

Accepted Answer

The answer of What is the average power dissipation in...

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 series circuit contains a resistor of 20 W, a capacitor of 0.75 mF and an inductor of 120 mH.What frequency should be used to create a resonance condition in the circuit?
A)160 Hz
B)320 Hz
C)640 Hz
D)530 Hz

Accepted Answer

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

Question 17

A series RLC AC circuit is at resonance.It contains a resistor of 30 W, a capacitor of 0.35 mF and an inductor of 90 mH.If an effective (rms) voltage of 150 V is applied, what is the effective (rms) current when the circuit is in resonance?
A)3.3 A
B)5.0 A
C)9.4 A
D)16.1 A

Accepted Answer

At resonance, the reactance of the capacitor and inductor cancel each other out, leaving only the resistance in the circuit. The resonant frequency can be found using the formula f = 1 / (2π√LC), where L is the inductance (90 mH) and C is the capacitance (0.35 mF).

f = 1 / (2π√(0.00009 * 0.00035)) = 1591 Hz

The impedance of the circuit at resonance is just the resistance, which is 30 Ω. The effective current can be found using Ohm's law:

I = V / Z = 150 V / 30 Ω = 5 A

Therefore, the answer is B) 5.0 A.

Question 18

A series RLC circuit has a inductive reactance of 4 W and a capacitive reactance of 1/4 W. By what factor should the AC frequency be changed to put this circuit into resonance?
A)4
B)1/4
C)1/2
D)This circuit cannot be made to achieve resonance.

Accepted Answer

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

Question 19

Maxwell developed his theory of electromagnetism by combining previous discoveries.He added his own original hypothesis that:
A)electric charges produce electric fields.
B)moving electric charges produce magnetic fields.
C)changing electric fields produce magnetic fields.
D)changing magnetic fields produce electric fields.

Accepted Answer

The answer of Maxwell developed his theory of electromagnetism by...

Question 20

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's equations, published in 1865, predicted that electromagnetic waves could propagate through space at the speed of light. This insight laid the foundation for the development of radio communication and many other technologies.

Quiz 21: Alternating Current Circuits and Electromagnetic Waves

An AM radio tuning circuit has a coil with an inductance of 6.00 mH and a capacitor set at 7.50 * 10^-6 mF.What frequency will it detect?

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

The primary winding of an electric train transformer has 400 turns, and the secondary has 50.If the input voltage is 120 V(rms) , what is the output voltage?

An AC power generator produces 25 A (rms) at 3 600 V.The energy is transmitted through a long-distance power line, which has a total resistance of 100 W.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 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 80 turns, how many turns must the secondary have?

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

A series RLC circuit in a radio is in resonance with AM 600 kHz.If the radio station is changed to AM 1 200 kHz, by what factor must the capacitance be multiplied to again achieve resonance?

An FM radio tuning circuit has a coil with an inductance of 0.003 0 mH.What is the value of the capacitance if the set is tuned to 98 MHz?

An AC power generator produces 50 A (rms) at 3 600 V. The voltage is stepped up to 100 000 V by an ideal transformer, and the energy transmitted through a long-distance power line with a total resistance of 100 W.What is the rms current in the long-distance line?

A transformer consists of a 500-turn primary coil and a 2 000-turn secondary coil.If the current in the secondary is 3.00 A, what is the primary current?

Find the resonant frequency for a series RLC circuit where R = 20.0 W, C = 10.0 µF, and L = 4.0 mH.

An AC series circuit contains a resistor of 20 W, an inductor of 30 mH and a variable capacitor.If the frequency of the applied voltage is 500 Hz, to what setting should the capacitor be set if resonance is achieved?

An ideal transformer is one that:

What is the average power dissipation in an RLC series circuit in which R = 100 W, L = 0.1 H, and C = 10 µF driven at resonance by a 100-V (rms) source?

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

An AC series circuit contains a resistor of 20 W, a capacitor of 0.75 mF and an inductor of 120 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 30 W, a capacitor of 0.35 mF and an inductor of 90 mH.If an effective (rms) voltage of 150 V is applied, what is the effective (rms) current when the circuit is in resonance?

A series RLC circuit has a inductive reactance of 4 W and a capacitive reactance of 1/4 W. By what factor should the AC frequency be changed to put this circuit into resonance?

Maxwell developed his theory of electromagnetism by combining previous discoveries.He added his own original hypothesis that:

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