Question 1

An ac current is inversely proportional to an ac voltage.

Accepted Answer

An ac current is not inversely proportional to an ac voltage. Instead, the relationship between current and voltage in an AC circuit is determined by the impedance which is a combination of resistance, capacitance, and inductance.

Question 2

Commercial line voltages are usually square waves at a frequency of 60 Hz.

Accepted Answer

Commercial line voltages are usually sinusoidal waves at a frequency of 60 Hz.

Question 3

Rise time, fall time, and duty cycle are all terms associated with sine wave measurement.

Accepted Answer

Rise time and fall time are terms associated with square wave measurement, while duty cycle is a term associated with pulse wave measurement. None of these terms are specifically associated with sine wave measurement.

Question 4

One complete sine wave contains 360°.

Accepted Answer

This is true. One complete sine wave oscillates from 0° to 360°.

Question 5

-Which of the following can be measured from points B to F in Figure 8 -1?
A)the angle
B)the peak -to -peak voltage
C)the frequency
D)the period

Accepted Answer

The answer of  
-Which of the following can be...

Question 6

The term RMS stands for "root -mean -square."

Accepted Answer

RMS does indeed stand for "root-mean-square."

Question 7

Kirchhoff's voltage law can be used with resistive ac circuits.

Accepted Answer

Kirchhoff's voltage law can be used with resistive ac circuits to determine the voltages across different elements in the circuit.

Question 8

A sine wave's peak value is smaller than its RMS value.

Accepted Answer

The peak value of a sine wave is equal to √2 times its RMS value, so the peak value is actually larger than the RMS value.

Question 9

Only frequency increases with the speed of an AC generator.

Accepted Answer

Frequency is determined by the speed of rotation and the number of poles in the generator. The speed of the generator affects the voltage and current output, but not the frequency.

Question 10

7.07 VPP is approximately equal to 2.5 VRMS.

Accepted Answer

7.07 VPP is the peak-to-peak voltage, which is the difference between the maximum and minimum voltage values. 2.5 VRMS is the root mean square voltage, which is the square root of the average of the squared voltage values. For a sine wave, the peak-to-peak voltage is approximately 2.83 times the RMS voltage, so 7.07 VPP is approximately equal to 2.5 VRMS.

Question 11

Current flows both ways simultaneously in an AC circuit.

Accepted Answer

The answer of Current flows both ways simultaneously in an...

Question 12

-Which one of the following represents the value at point G in Figure 8 -1?
A)the peak voltage
B)the RMS voltage
C)the frequency
D)the period

Accepted Answer

The answer of  
-Which one of the following represents...

Question 13

What is the instantaneous voltage at 42° on a 230 VP sine wave?
A)149 V
B)154 V
C)115 V
D)76.1 V

Accepted Answer

The answer of What is the instantaneous voltage at 42°...

Question 14

20 Vrms of alternating current will illuminate a given lamp at the same intensity as 20 V of direct current.

Accepted Answer

The RMS (Root Mean Square) value of AC represents the equivalent DC voltage that would produce the same amount of heat or light in a given device. Therefore, 20 Vrms of AC and 20 V of DC would have the same effect on the illumination of a lamp.

Question 15

The period of a 5 Hz wave form is 200 ms.

Accepted Answer

The answer of The period of a 5 Hz wave...

Question 16

A sine wave's frequency equals the reciprocal of its period.

Accepted Answer

This is true. The frequency of a sine wave can be calculated by dividing 1 by its period.

Question 17

The higher a sine wave's frequency, the shorter its period.

Accepted Answer

This is because period is inversely proportional to frequency, meaning as one increases the other decreases. Therefore, a higher frequency corresponds to a shorter period.

Question 18

Single -phase power cannot be converted to three -phase power.

Accepted Answer

Single-phase power can be converted to three-phase power using devices such as phase converters or variable frequency drives.

Question 19

RMS is another name for peak.

Accepted Answer

RMS (Root Mean Square) is a measure of the average power of a signal, whereas peak refers to the highest point or level of a signal. They are not interchangeable terms.

Question 20

The RMS value of a sine wave means .
A)the root mean square value
B)the heating effect of an ac generator of the same voltage
C)the same as IPP × R
D)the same as IP × R

Accepted Answer

The RMS (Root Mean Square) value of a sine wave is a measure of its amplitude that is equivalent to the DC voltage that would produce the same heating effect in a resistor. It is calculated by taking the square root of the mean of the squared values of the sine wave over one period. This value is commonly used in electrical engineering to describe the power of an AC signal.

Quiz 8: Introduction to Alternating Current and Voltage