Definitions in AC Theory

Note

Only sinusoidal AC supply are considered in s1.

Say is alternating as in .

Peak value

Maximum instantaneous value. in the example.

Peak-to-peak value

Maximum variation between maximum positive and negative instantaneous values. in the example.

For a sinusoidal waveform, this is twice the peak value.

Mean value

Here:

• is the starting time of a cycle
• is the periodic time

For any symmetric waveform, mean value is .

Average value

Mean value of the rectified version of a waveform.

For symmetric waveforms, half-cycle mean value is taken as the average value.

For sinusoidal waveforms, from the example:

Effective value or rms (root mean square) value

For sinusoidal waveforms:

Note

is the equivalent current that dissipates same amount of power across a resistor in time as . Similar for voltage.

Note

rms value is always used to express the magnitude of a time varying quantity.

Instantaneous power

Form factor

Peak factor