1. Electricity and Magnetism
Physics 208
Dr. Tatiana Erukhimova
Lectures 31, 32

2. Induced EMF and Inductance
1830s Michael Faraday
Joseph Henry

3. Faraday’s Law of Induction
The induced EMF in a closed loop equals the negative of the time rate of change of magnetic flux through the loop

4. There can be EMF produced in a number of ways:
A time varying magnetic field
An area whose size is varying
A time varying angle between and
Any combination of the above

6. From Faraday’s law: a time varying flux through a circuit will induce an EMF in the circuit. If the circuit consists only of a loop of wire with one resistor, with resistance R, a current R
Which way?
Lenz’s Law: if a current is induced by some change, the direction of the current is such that it opposes the change.

8. The Moving Circuit
There is a uniform magnetic field out of the board. A rectangular circuit is pulled at a constant speed to the right. What current flows in the circuit if the total resistance of the circuit is R?

9. Exercise 4

10. The magnetic field between the poles of the electromagnet is uniform, but its magnitude is increasing at the rate of T/s. The area of the conducting loop in the field is 120 cm2, and the total circuit resistance, including the meter and the resistor, is 5.0 Ώ. Find the induced EMF and the induced current in the circuit.

11. A Simple Generator

12. Induced EMF and Inductance
1830s Michael Faraday
Joseph Henry
M is mutual inductance