Electro-Magnetic Induction © D Hoult 2008

EMF induced in a conductor moving through a uniform magnetic field

The wire moves distance Ds in time Dt. In this time, a charge Dq moves past any point in the wire.

The wire moves distance Ds in time Dt. In this time, a charge Dq moves past any point in the wire. work done = F Ds

The wire moves distance Ds in time Dt. In this time, a charge Dq moves past any point in the wire. work done = F Ds F Ds work done per unit charge = Dq

The wire moves distance Ds in time Dt. In this time, a charge Dq moves past any point in the wire. work done = F Ds F Ds work done per unit charge = Dq work done per unit charge is the induced emf

If the wire moves at constant speed, the force F must be

If the wire moves at constant speed, the force F must be equal but opposite to the force acting on it due to the current I, induced in it

If the wire moves at constant speed, the force F must be equal but opposite to the force acting on it due to the current I, induced in it F = - I L B

If the wire moves at constant speed, the force F must be equal but opposite to the force acting on it due to the current I, induced in it F = - I L B F Ds E = Dq

If the wire moves at constant speed, the force F must be equal but opposite to the force acting on it due to the current I, induced in it F = - I L B F Ds E = Dq -ILB Ds E = Dq

I =

Dq I = Dt

Dq - (Dq/Dt) L B Ds I = E = Dt Dq and

Dq - (Dq/Dt) L B Ds I = E = Dt Dq and Ds = Dt

Dq - (Dq/Dt) L B Ds I = E = Dt Dq and Ds = v Dt

Dq - (Dq/Dt) L B Ds I = E = Dt Dq and Ds = v Dt E = - B L v