# What happens when a wire is placed within a magnetic field?

Jan 27, 2016

If there is no current flowing in the wire, nothing happens. If there is a current flowing, a force will act on the wire.

#### Explanation:

When charged particles are stationary in a magnetic field, no force acts on them. The electrons in a wire are charged particles, but if there is no current flowing in the wire to make the electrons move, there is no net movement, so there is no force. (the electrons may move around randomly, but as many move one way as move the other so the forces all cancel)

If there is a current flowing, there will be a force acting. On an individual charge this is given by:

$F = q v B \sin \theta$ where

$F$ is the force $\left(N\right)$
$q$ is the charge $\left(C\right)$
$B$ is the magnetic field strength $\left(T\right)$
$\theta$ is the angle between the velocity and the field

For a wire carrying a current, $I$, where a length $l$ of the wire is in the magnetic field, this becomes:

$F = B I l \sin \theta$