Question

What is the expression of AC over an half cycle ?

Answer 1

The average value of a whole sinusoidal waveform over one complete cycle is zero as the two halves cancel each other out, so the average value is taken over half a cycle. The average value of a sine wave of voltage or current is 0.637 times the peak value, (Vp or Ip.

Answer 2

Current is a measurement of the flow of electrons. An ampere (amp) is actually how many coulombs (6.241 x 10^18 electrons) move through a single point every second. There are a few different types of current, the most common two being AC and DC. While typical batteries produce a current that only moves in one direction (DC), power is transferred over long distances and into homes by way of alternating current (AC).

Alternate literally means to pass back and forth from one state to another, and with electricity, this happens in the direction of the current. For half of the cycle, the current flows in one direction; it then switches direction and flows backwards