1. AP Physics Chapter 21 Electromagnetic Induction, Faraday’s Law, and AC Circuits An electric current produces a magnetic field and a magnetic field exerts a force on an electric current or moving electric charge.

2. 21-2 Induced EMF Michael Faraday (1791-1867) Faraday found that an induced emf is produced by a changing magnetic field. See diagram on p623 A constant B induces no emf.

3. 21-2 Faraday’s Law of Induction; Lenz’s Law The more rapidly the magnetic field changes, the greater the induced emf. But the emf is proportional to the rate of change of magnetic flux f B. f B =BA=BAcos q E =-N f B =BA=BAcos q Lenz’s law …an induced emf always gives rise to a current whose magnetic field opposes the original change in flux. See Examples 21-2-21-3 p626-627

4. HOMEWORK P652 Q1-4 Pg 654 PR#1-2 due Friday BOP