1. Electro-Magnetic Induction
© D Hoult 2008

2. EMF induced in a conductor moving through a uniform magnetic field

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

9. 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

10. 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

11. 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

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

13. 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

14. 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

15. 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

16. 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

17. I =

18. Dq
I = Dt

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

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

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

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