Alternating Current

Question 1

The most common of all AC waveforms is the ________

Answer 1

Sine wave

Question 2

The sine wave contains a total of 360 electric degrees. It reaches its peak positive voltage at ________, returns to a value of 0 volts at ________, increases to its maximum negative voltage at ________, and returns to 0 volts at ________

Answer 2

90 degrees, 180 degrees, 270 degrees, 360 degrees

Question 3

Each complete waveform of 360 degrees is called a ________

Answer 3

Cycle

Question 4

The number of complete cycles that occur in 1 second is called the ________ and is measured in ________

Answer 4

Frequency; hertz (Hz)

Question 5

The ________ is measured from the maximum value in the positive direction to the maximum value in the negative direction

Answer 5

Peak-to-peak value

Question 6

The ________ is measured from zero to the highest value obtained in either the positive or negative direction

Answer 6

Peak value, or amplitude

Question 7

The ________ at any point on a sine wave is equal to the peak, or maximum voltage times the sine of the angle of rotation

Answer 7

Instantaneous voltage

Question 8

The ________ of voltage will produce as much power as a like amount of DC voltage

Answer 8

RMS value

Question 9

The ________ and ________ in a pure resistive circuit are in phase with each other

Answer 9

Current; voltage

Question 10

The ________ of voltage is used when an AC sine wave is changed into DC

Answer 10

Average value

Question 11

_______ can be produced only when current and voltage are both positive or both negative

Answer 11

True power, or watts

Question 12

Resistance in AC circuits is characterized by the fact that the resistive part will ________

Answer 12

Produce heat

Question 13

Name the three basic types of AC loads

Answer 13

Resistive, inductive, and capacitive

Question 14

In an AC circuit, the ________ is a phenomenon that causes electrons to be forced to the outer surface of conductors by the AC induced eddy currents

Answer 14

Skin effect

Question 15

How many degrees are there in one complete sine wave?

Answer 15

360 degrees

Question 16

At what angle does the voltage reach its maximum negative value on a sine wave?

Answer 16

270 degrees

Question 17

What is frequency?

Answer 17

Frequency is the number of cycles per second in an AC sine wave. It is the rate at which current changes direction per second and is measured in hertz

Question 18

Give the formula which is used to determine the instantaneous value at any point along a sine wave

Answer 18

E(inst) = E(max) x sinϴ

Question 19

Give the formula used to calculate the time necessary for a waveform to complete one cycle

Answer 19

T = 1 / f, where T = time in seconds and f = frequency in Hz

Question 20

What are the formulas for determining RMS and peak values?

Answer 20

RMS = peak x 0.707

peak = RMS x 1.414

Question 21

For a full wave rectified sine wave, what formula is used to determine the average value of voltage?

Answer 21

E(av) = 0.637 x E(max)

E(av) = 0.9 x RMS

Question 22

________ is the distance the radiating field or signal can travel during one cycle of alternating voltage

Answer 22

Wavelength

Question 23

Calculating wavelength is done using which formula?

Answer 23

Wavelength(λ) = 300,000,000 (speed of light in metres per second) / frequency