# EMF & potential difference

Explains "voltage"

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• Created by: Rachel
• Created on: 11-04-09 13:43

## What is EMF?

Electromotive Force is the amount of energy supplied per unit charge by an energy source (usually a cell in an electric circuit)

EMF is measured in Volts- (V)

It can be worked out by dividing energy supplied (J) by the amount of charge (C)

An energy source/source of EMF is needed to make an electric current flow

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## Potential Difference

Pd is also measured in Volts (V) BUT describes the energy transferred FROM the charge TO an appliance or component in the circuit

So effectively

potential difference = work done (J) / charge (C)

The total EMF in a ciruit = total potential difference, so all energy supplied is transferred back to components over the course of a circuit

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## Measuring EMF/pd

A voltmeter is used to measure EMF/pd, and must be connected in parallel with the component- potential difference is measure across a component, current is measure through it

Computers are often used to record potential difference or current readings because they can take more readings in a small space of time, and the readings are less likely to have errors

Software can then be used to plot graphs quickly and easily

Computer improve reliability and validity of data

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