3. Review p. 76 #12

4. Electromagnetic Induction
Topic 12.3/12.4

5. Outcomes
You will describe how the discoveries of Oersted and Faraday form the foundation of the theory relating electricity to magnetism
You will describe, qualitatively, the effects of moving a conductor in an external magnetic field, in terms of moving charges in a magnetic field.

6. Can a magnetic field produce an electric current?
After Oersted discovered that an electric current produces a magnetic field, many scientists investigated if a magnetic field could produce an electric current
It can!
Electromagnetic induction
Induced current

7. Hand Rule
The direction of the current can be predicted by using the “third” hand rule:
Fingers: direction of the magnetic field
Thumb: direction of motion of the wire
Palm: direction of the force on the electrons in the wire

8. Sample Problem
In what direction is the induced electron flow flowing in this circuit?
CLOCKWISE

9. Faraday’s Apparatus & Lenz’s Law
Faraday discovered that when the switch of his induction coil was closed or opened, the galvanometer deflected, indicating that a brief current passed through the secondary coil
If the switch remained opened or closed there would be no detection on the galvanometer

10. Faraday’s Apparatus & Lenz’s Law
An electric current is produced (induced) in the solenoid when it is moving relative to the magnetic field
The galvanometer will deflect in different directions, depending on the movement of the magnet and the solenoid
The direction of the induced current can be found using Lenz’s law

11. Lenz’s Law
Lenz’s law is an application of the law of conservation of energy
MUST DO WORK AGAINST THE SYSTEM TO GAIN ENERGY
For example, when a magnet is pushed into the coil, a current is induced in the coil. Lenz’s law indicates that the current will flow so that the magnetic field inside the coil opposes the magnetic field of the magnet.
“Making it difficult…”

12. Sample Problem
In what direction is the induced current (electron flow) through point G?
LEFT

13. Sample Problem
In what direction is the induced current (electron flow) through point G?
LEFT

14. Sample Problem
In what direction is the induced current (electron flow) through point G?
RIGHT

15. Homework Concept Qs: p. 620 #3, 6 & 7
Calculation Qs: p. 65 #25 – 28 (workbook)
Hand Rule Worksheet