MagnetismMagnetic Force

1

Magnetic Force on a Moving Charge

Magnetic Force on a Current Carrying Wire

MagnetismMagnetic Force

2

1. Point the fingers of your right hand in the direction of the vector A.

2. Curl your fingers toward the direction of the vector B.

3. The cross-product vector C is given by the direction of your thumb.

A

B C

MagnetismMagnetic Force

3

Magnetic Force on Charge Particles

the charge must be moving relative to the magnet creating the magnetic field.

the velocity of the charge must not be parallel to the direction of the magnetic field.

The force due to the magnetic field on a moving charge is

BvF q

The force on a positive charge has a direction given by the right-hand rule and has the magnitude qvB. For a negative charge the direction reverses.

The SI units of magnetic field are Tesla (T) or Gauss.(1 Gauss = 10-4 T)

sinF q vB

MagnetismMagnetic Force

4

Begin with the force on each element of charge

F v Bq

The total charge (remember that they are electrons) passing through the wire in a given time dt is given by

I

q I t The speed of the electrons as they move through the wire is

vL

t

So that

vL

q I t ILt

IL B

L

sinF ILB