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Old 10-19-2009, 05:57 PM   #23 (permalink)
micondie
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Quote:
Originally Posted by jamesqf View Post
Sure. I was trying to give a simplistic explanation, without invoking Kirchoff's Law &c. But try a simple experiment: take a 12-volt battery, and connect a piece of copper wire (low resistance) between the terminals. Lots of current flow, heat, sparks, etc - and in particular energy "burned up". Now put a piece of wood (very high resistance) between the terminals. Does the wood start to smoke & catch fire from all the energy it's burning up? No, because current isn't flowing because of the resistance.

ETA: Or consider the transistor: it's a device that's switchable between two states, high and low resistance. When it's in the high resistance state, is it "burning up" the power that's not flowing through it?
Try your experiment with a piece of #24 or finer wire but be careful because it it going to get HOT!!!!!!!!
The reason a piece of wood won't get hot is that there is no current flowing through it to generate any.
Why do you think they mount power transistors on a heat sink?
Why is your CPU mounted on a heat sink with a fan?
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