Simple Electricity Question

[jerryyu]

when you plug a power cord into an outlet, but when you don't connect that power cord into (let just say a laptop) where does that energy goes? Do all of those energy transforms to heat?

I heard of the term "save energy, and unplug your electronic when they're not in use"(or something close to that) a lot.

[TonyMcC]

I think the advice given is don't leave transformers or small power supply units such as used by mobile phones plugged into a power socket when you are not using them. These devices use a small amount of power under these circumstances. The power they take creates heat. As the amount of power they take is small the temperature rise will also be small. It is much the same as leaving equipment such as television sets on standby. To answer your question - if you leave your power cord alone connected to a power socket it will take a tiny amount of power, really so tiny it can be ignored under normal circumstances. The reason is that a tiny electric current will flow due to capacitance between the wires and this tiny current will in turn generate a tiny amount of heat in the wires due to their resistance.

[Mr Skeptic]

Plugging a regular extension cord or power strip into an outlet shouldn't really have much of an effect. I suppose there would have to be some loss due to the extra length and the fact that we use alternating current, but nothing significant. However, if it has a (dumb) transformer on it, the transformer will keep functioning even without a load and will lose some of that energy. You can tell because they'll be warm. The warmer it is, the more power it is wasting.

[jerryyu]

how about a surveillance camera, are they energy-consuming since they are to be leave on (not standby) for 24 hours a day?

[TonyMcC]

Yes - a small amount. I would say that as a general rule anything you find useful that uses electricity will cost you (or in some cases someone else) money. I'm afraid it's a case of nothing for nothing!

Edited October 31, 2010 by TonyMcC