1. Electromagnetic Induction and Faraday’s Law Physics Department, New York City College of Technology

2. Key words Induced emf Induced current Magnetic flux Right hand rule Faraday’s law Lenz’s law

3. Induced emf

4. Faraday repulsion coil Disc 20 #19 Disc 20 #20

5. Magnetic flux Magnetic flux is defined as The unit is Weber (Wb)

6. Faraday’s Law If the flux through N loops of wire changes by an amount ΔФ B over a brief time interval Δt, the induced emf is The minus sign indicates in which direction the induced emf acts.

7. Lenz’s Law A current produced by an induced emf moves in a direction so that its magnetic filed opposes the original change in flux.

8. Example #1 A square coil of 100 loops is pulled at constant speed. It takes 0.1s for the whole coil to reach the field- free region. The coil’s resistance is 100Ω.

9. Example #1—continued (a)

10. Example #1—continued (b)

11. emf induced in a moving conductor