# Current / Amperage

Discussion in 'General Electronics Chat' started by chomper, Mar 29, 2005.

1. ### chomper Thread Starter New Member

Mar 29, 2005
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I've read a few books on electronics including the one on this site and they all do a good job of providing information on voltage, but it seems like the information presented on current is a side thought. As a result I just can't seem to grasp the concept.

If I have a 9V battery and say I put it in series with a .01 ohm resistor (if I had such a thing) ohms law would state I should get 900 amps.

Also what is driving the current? If I wire the 9V battery in a short circuit what will my amperage be and what limits it?

It also seems like if something tries to draw more amperage then the source can supply at a given voltage - the voltage drops.

First off why is the load drawing an amperage?
Why does the voltage drop?

I apologize for this questions, but I'm hoping someone can help and clarify this in a way I can understand.

2. ### David Bridgen Senior Member

Feb 10, 2005
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It helps some people to think of voltage being similar to a pressure difference in a hydraulic system.

If there is a pressure difference across such a system a current (your "amperage")will flow. The magnitude of the current being limited by the diameter of the pipe/tubing. The smaller the diameter the higher its resistance to current flow.

If the pressure is increased the current increases proportionally.

A perfect voltage, or pressure, source has no internal resistance but practical ones have, especially dry cells and batteries.

In the case of a short circuit across a 9 volt battery the current would be limited by the battery's internal resistance. The relationship between the voltage, resistance and current would still obey Ohm's Law.

Dec 14, 2004
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