**Magnetic fields and forces**

A particle of charge
* q* moving with velocity

where q is the angle between the direction of the magnetic field and the direction of the velocity. The direction of the force is perpendicular to both the velocity and magnetic field: see the right-hand-rule page. If a particle moves parallel to the magnetic field, it feels no force.

The magnetic field is given in units
of * Tesla*, where
1.0

A wire carrying an electric current
has moving charge and therefore feels a force in a magnetic field.
If a segment of wire of length * L*
has

Thus the force per unit length felt by a
segment of wire in a magnetic field is the current times the magnetic field.
Like the original force equation, this also needs a factor of
**sin**** q
if the field and the wire are not perpendicular to each other.
**

*
Examples
Magnetic fields and forces index
Lecture index*