1. Electromagnetic Induction

2. A current carrying wire in a magnetic fieldS

3. What if…?

4. a.k.a. electromotive force or “emf”+
Induced Voltage
a.k.a. electromotive force or “emf” –

5. Induce voltage in a wire moving through a magnetic field
V = BvL
B = magnetic field strength (T, Tesla)
v = velocity of the wire (ms-1)
L = the length of wire in the field (m)

7. Induced current + –
I = V / R

8. Example – EM Induction
A metal rod is moved in a magnetic field. The rod is 24 cm long and moves at 8 ms-1. The magnetic field strength is 0.7 T. Calculate the induced voltage and the induced current of the rod.
R = 10 Ω

11. Demo – Induced Current

12. But wait!
Dragging a piece of wire in a magnetic field produces an induced voltage (and an induced current if it is a complete circuit)
Then you have a current carrying wire in a magnetic field
F = BIL ?

13. + –

14. F = BIL
F = BIL

15. Lenz’s Law
“The induced current always opposes the change/action producing it”
In this “wire in a B field” example, the induced current causes a force (F = BIL) which opposes the wire’s movement.
This law is a result of conservation of energy! Work must be done to generate electrical energy.

16. Example – Lenz’s Law
A metal rod is moved in a magnetic field. The rod is 24 cm long and moves at 8 ms-1. The magnetic field strength is 0.7 T. Find the size and the direction of the opposing force on the moving rod.
R = 10 Ω

17. Try now:
Homework Booklet “INDUCTION”
Question 19 (skip (h))
Question 17

18. Textbook Activity 20B
Worksheets #8 and #9

19. What about this?

20. + –

21. Generating Electricity

22. N S

23. N S

24. N S

26. What if…? N S

27. AC = Alternating Current

28. Demo: AC Generator

29. Hydroelectric Power