# The Motor Effect - Fridge Physics

A current-carrying wire or coil can exert a force on a permanent magnet. The force increases if the strength of the magnetic field and/or current increases. This is called the motor effect.

## Demo

In this tutorial you will learn how to calculate the force on a wire carrying a current in a magnetic field.

The equation is written like this:

$F = { \text B \; \text x \; \text I \; \text x \; \text L}$

## Chilled practice question

Calculate the force on a wire carrying a current of 3 A. 0.25 m of the wire is in the magnetic field. The magnetic flux density is 15 T.

## Frozen practice question

The force on a wire in a magnetic field is 30 N. The magnetic flux density is 3 T and the length of wire in the magnetic field is 50 cm. Calculate the current.

## Science in context

A current-carrying wire or coil can exert a force on a permanent magnet.The force increases if the strength of the magnetic field and/or current increases. This is called the motor effect.

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