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Q & A: voltage source

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Most recent answer: 10/22/2007
Q:
what is voltage source? And why is it called a voltage source?
- zoha (age 19)
NED UNIVERSITY, KARACHI,PAKISTAN
A:
A voltage source keeps about the same electrical voltge (sort of like electrical pushing strength) for a fairly wide range of things that it might be connected to. For example, a little battery will have 1.5 Volts between its terminals, so long as it's not hooked up to some very low-resistance circuit. In contrast, a current source produces some fixed electrical current so long as it's not hooked up to a very HIGH resistance circuit.

It's easier to picture with water flow. If you have a tall column of water, there will be some pressure difference betwen the top and bottom. If the water is allowed to flow through a tube attached to the bottom of the tall column, that pressure difference will be almost unchanged if the tube is small. That's like a voltage source. If the tube is so large that whatever supplies water to the upper end has trouble keeping up with the flow, the pressure difference will drop.

If you have a long river running downhill, the flow through some channel won't depend much on whether the channel is wide or narrow. That's like a current source. Of course if the channel gets really narrow, then it will be able to slow the flow some.

Mike W.

(published on 10/22/2007)

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