There are several examples that could help, but one of the simplest is to
consider a light bulb. It does not matter which way the current goes
through the light bulb. The filament will heat up and the light bulb will
light up if the current goes either direction. This means the AC power
source provides energy to the filament during both halves of the cycle. In
order to cancel out, the light bulb would have to receive energy during
one-half the cycle, then return energy to the power source during the other
half cycle. That would imply the filament gets hot and radiates energy
during one-half cycle, but gets cold and absorbs energy during the half
cycle. I think we all know it doesn't work that way. Experimenting with a
light bulb and battery shows that the filament heats up and radiates energy
regardless of which way the current flows.
Most electrical devices work this way either naturally (such as the light
bulb) or by design (such as an AC-to-DC power supply in which clever
rectifier circuits make use of both halves of the AC cycle).
Michael D. Edmiston, Ph.D. Phone/voice-mail: 419-358-3270
Professor of Chemistry & Physics FAX: 419-358-3323
Chairman, Science Department E-Mail edmiston@bluffton.edu
Bluffton College
280 West College Avenue
Bluffton, OH 45817
I know that AC delivers energy - that is obvious.
But I still have trouble understanding how this is possible
since half the time the potential is positve and the other
have it is negative. It seems they should cancel out.
I know and can do the rms (root mean squared - although
shouldn't it be squared mean root) for figuring out various
quantities, but I still don't think I have a basic
understanding on "how" it really works.