M3.13

Question 1

What are the two main characteristics of AC that distinguish it from DC?

Answer 1

• The amount (size) of both teh voltage and current changes with time
• The direction (polarity) of both the voltage and current changes with time

Question 2

What can be said about common AC?

Answer 2

• The changes repeat continuously
• The average voltage and current are both zero
• The voltage and current vary sinusoidally

Question 3

What makes up an AC cycle?

Answer 3

A full positive and negative alternation

Question 4

What is phase?

Answer 4

The phase of a periodic waveform is a measure of the fraction of the cycle that has been completed at a particular point on the x-axis.

Question 5

What is phase offset?

Answer 5

The difference between the origin and where the cycle begins. For example is the cycle passes through the origin the phase offset is 0.

Question 6

What is a period?

Answer 6

The time taken for one complete cycle

Question 7

What is frequency?

Answer 7

Frequency is the number of cycles completed per second.

Question 8

Where is amplitude measured from and to?

Answer 8

Equilibrium (0) to the peak

Question 9

How can work done be calculated for an AC current?

Answer 9

An approximation to this value can be found by summing equally spaced instantaneous values of a half cycle.

Question 10

What the the root mean squared value of an AC volatge?

Answer 10

The value that when applied to a resistance, will produce teh sma empower output as an equivalent DC voltage.

Question 11

What is a peak-to-peak value?

Answer 11

Twice the peak value i.e. the value measured between positive and negative maximum values.

Question 12

How do you calculate RMS?

Answer 12

Divide peak current/voltage by root 2 or multiply by 1/root 2 (=0.707)