1. Electromagnetic Induction (EMI) AP Physics

2. Electromagnetic Induction (EMI) A changing magnetic field can induce a current in a circuit called the induced current. The corresponding emf that must be present to cause the current is the induced emf.

3. What Causes Induction

4. Magnetic Flux ( φ m ) The amount of magnetic field there is in an area. (The number of magnetic field lines in an area.) Units of φ m : Only the components of magnetic field that are perpendicular to the area contribute to the flux. θ

5. Magnetic Flux ( φ m ) θ θ θ

6. Faraday’s Law But wait…to have induction there must be a change in the magnetic field (therefore a change in the magnetic flux)!! “The induced emf in a circuit equals the rate of change of the magnetic flux through the circuit.”

7. Flux Problem The U-shaped conductor lies perpendicular to a uniform magnetic field B with magnitude B = 0.60 T, directed into the page. We lay a metal rod with length L = 0.10 m across the two arms of the conductor, forming a conducting loop, and move the rod to the right with constant speed v = 2.5 m/s. What is the magnitude of the resulting emf?

8. Generators A device that converts mechanical energy to electrical energy. Alternating current generator (alternator)

9. Lenz’s Law “The direction of any magnetically induced current or emf is such as to oppose the direction of the phenomena causing it.”

10. Lenz’s Law Lenz’s Law requires some thinking!

11. Motional emf The induced emf in a circuit equals the rate of change of the magnetic flux through the circuit.

12. Transformers A device that converts voltage.

13. Power Transmission

14. Physics Rock Band Electromagnetic Induction is used to ROCK OUT!! Microphones

15. Physics Rock Band Electromagnetic Induction is used to ROCK OUT!! Electric Guitar

16. Physics Rock Band Electromagnetic Induction is used to ROCK OUT!! Cassette Tapes (kickin’ it old school)