Why do my speakers hum when I unplug my computer?

Question

I have my PC plugged into the back of my receiver with a 3.5 jack that converts to a set of AV jacks. When I unplug the line from the PC I get a humming in the speakers....

Answer 1

It's called 60 cycle hum. If there's no audio input they will give off a hum from the power source. It's nothing to worry about. Do you remember the first scene from, " Back to the Future 1",  where Marty turned up the speaker, just before he hit the power cord on his guitar? That's 60 cycle hum! Although I usually don't link to Wikipedia, it has the more scientific answer:http://en.wikipedia.org/wiki/Mains_hum

Even spell check doesn't like it!