Question 1

The rms current is equal to the direct current that:

Accepted Answer

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.

Question 2

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

Accepted Answer

A) 282 V 
B) 200 V 
C) 141 V 
D) 100 V

Question 3

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

Accepted Answer

A) 2.1 * 10-3 s 
B) 4.2 * 10-3 s 
C) 8.3 * 10-3 s 
D) 1.7 * 10-3 s

Question 4

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?

Accepted Answer

A) 5.31 A 
B) 9.23 A 
C) 10.8 A 
D) 26.0 A

Question 5

In a capacitor in an AC circuit, the voltage:

Accepted Answer

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.

Question 6

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

Accepted Answer

A) 1/2 
B) 1/4 
C) 2 
D) 4

Question 7

Maxwell guessed that visible light was an electromagnetic wave because of its:

Accepted Answer

A) frequency. 
B) wavelength. 
C) speed. 
D) energy.

Question 8

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?

Accepted Answer

A) 4 
B) 1/4 
C) 1/2 
D) This circuit cannot be made to achieve resonance.

Question 9

An ideal transformer is one that:

Accepted Answer

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.

Question 10

Which condition of motion must be met with regard to a charged particle if it is in the process of emitting electromagnetic radiation?

Accepted Answer

A) moves at constant velocity 
B) accelerates 
C) moves at the speed of light 
D) moves parallel to a uniform magnetic field

Question 11

Glass panes are opaque to a certain type of radiation, which passes through quartz.What type of radiation is it? This radiation is important in ozone layer reactions.

Accepted Answer

A) microwave 
B) gamma 
C) x-ray 
D) ultraviolet

Question 12

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

Accepted Answer

A) resistance equals capacitive reactance 
B) resistance equals inductive reactance 
C) capacitive reactance equals inductive reactance 
D) capacitive reactance equals zero

Question 13

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

Accepted Answer

A)   A 
B)   A 
C) (1/2) A 
D) None of the above.

Question 14

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

Accepted Answer

A) 240 V 
B) 170 V 
C) 120 V 
D) 85 V

Question 15

A monochromatic light wave in vacuum has frequency f0 and wavelength l0.Which of the following are also possible frequency and wavelength combinations for a monochromatic light wave in vacuum?

Accepted Answer

A) 2f0, 2l0 
B) f0/2, l0/2 
C) 2f0, l0/2 
D) None of the above are possible.

Question 16

What is the maximum value of the electric field E at 1.0 m from a 100-W light bulb radiating in all directions? (µ0 = 4p * 10-7 T*m/A, c = 3.00 * 108 m/s)

Accepted Answer

A) 77 V/m 
B) 2 000 V/m 
C) 4 000 V/m 
D) 6 000 V/m

Question 17

The electric field,  , in an electromagnetic wave is oriented in what direction with respect to its associated magnetic field,  ?

Accepted Answer

A)   parallel to
 
B)   anti-parallel to
 
C)   perpendicular to
 
D)   at a 45$\degree$ angle to

Question 18

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

Accepted Answer

A) 1/3 
B) 1.0 
C) 1.73 
D) 3.0

Question 19

The Doppler shift for electromagnetic radiation from distant galaxies moving away from the observer is called a:

Accepted Answer

A) red shift. 
B) blue shift. 
C) black shift. 
D) vacuum shift.

Question 20

A solar cell has a light-gathering area of 10 cm2 and produces 0.20 A at 0.80 V (dc) when illuminated with sunlight of intensity 1 000 W/m2.What is the efficiency of the solar cell?

Accepted Answer

A) 16% 
B) 7% 
C) 23% 
D) 4%

Exam 21: Alternating Current Circuits and Electromagnetic Waves