# Ohm's law

Ohm's law says that the current through a conductor is proportionate to the voltage across it. These cards show the ins and outs of Ohm's law.

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• Created by: Emily
• Created on: 21-11-11 11:24

## Ohm's law itself

Ohm's law simply states that the current in a cicuit is proportionate to the voltage across it and determined by the resistance of the circuit. However, this can be tricky for a number of reasons;

• It only works for certain types of conductors
• Electric current heats a wire, increasing the resistence, changing things

This means that although Ohm's law is simple, its not always going to be best. But the equation this gives is this;

Current= voltage/ resistance.

But this is not to last.

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## Current= voltage/ resistance. Except it doesn't...

So, Ohm's law tells you that if there's a 10V battery with 5 ohms resistance, the current is 2A. But here's the catch. 10V of electricity will make your wire get hot under the collar.

Look at it like this;

A runner is in a race. Their speed will be equal to the distance travelled divided by the time taken to travel that distance. However, maintaining that speed adds a new factor; the amount of energy the runner has. The runner can't keep up the speed and slows down. The distance travelled in a set time therefore changes. So he gets slower, bringing down distance travelled in that time. An outside factor has changed the rules.

The runner's speed represents the current, the distance travelled, the voltage and the time taken, the resistance. The example is showing how an external factor changes it up. The external factor we have here is heating of the wire from the current passing through it, increasing resistance. So its complicated.

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## And its picky too...

Ohm's law won't apply for everything. Only certain types of conductors. I'm afraid this means that Ohm's law has no bearing on the cheese or the wooden board you serve it on. Dang.

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