Steps 1. Move magnet into solenoid 2. Leave the magnet in solenoid 3. Move magnet out of solenoid
Variables Dependent: (1) Deflection of galvanometer pointer (2) Direction of deflection (3) Magnitude of deflection Independent: Pole of magnet Number of turns in solenoid Strength of magnet Cross-sectional area of solenoid Speed of magnet being moved in and out
Results (1) Deflection of galvanometer pointer Deflects: magnet is moving in and out of solenoid Does not deflect: magnet remains stationary in solenoid Current is flowing through circuit only when the magnet is moving in and out of the solenoid
Conclusion A varying magnetic field produces an e.m.f, which produces an induced current in a closed circuit.
Results (2) Direction of deflection Action of Bar Magnet Direction of Deflection Direction of e.m.f N-pole insertedRightAnti-clockwise N-pole withdrawnLeftClockwise S-pole insertedLeftClockwise S-pole withdrawnRightAnti-clockwise
Conclusion Lenz’s Law The direction of the induced emf, and thus, the induced current in a closed circuit, is always such that the magnetic effect always opposes the change producing it. Why oppose? – In Work, Energy, Power: GPE = KE – In Electromagnetic Induction: GPE = KE + Electrical energy – KE decreases for the conservation of energy
Results (3) Magnitude of deflection Increase in number of turns in solenoid strength of magnet cross-sectional area of solenoid speed of magnet being moved in and out Increases deflection – increases emf N Φ B Rate
Conclusion Faraday’s Law of Induction Where ℰ is the emf Induced emf generated in a conductor is proportional to the rate of change of magnetic flux vector linking the circuit.