13.1 Electromagnetic Induction

Electromagnetic Induction The production of current in a conductor moving through a magnetic field Law of Electromagnetic Induction A change in magnetic field in the region of a conductor induces a voltage in the conductor, causing a induced current.

Faraday’s Experiment Two circuits connected by an iron ring Primary circuit has a power source which produce a current that induces a magnetic field in the iron ring. The change in magnetic field in the iron ring induces a current in the secondary circuit.

Factors Increasing Electromagnetic Induction Coiled conductors vs straight conductors Increasing number of loops Increasing the rate of change of the magnetic field (sliding magnet in and out quicker) (Faraday-increase current more quickly in the primary circuit) Increasing the strength of the inducing magnetic field (stronger magnet) (Faraday-higher current in primary circuit)

Applications Generators Transformers Induction cooking (induces an electric current in the pot/pan) Metal detectors (induce an electric field in metal being detected) Induction chargers (electric toothbrush)

13.2 Lenz’s Law

Direction of Induced Current Heinrich Lenz formulated a law to describe the direction of the induced current. If the changing magnetic field induces a current in a coil, the electric current is in such a direction that its own magnetic field opposes the change that produced it. The coil opposes whatever the magnet is trying to do http://k12resources.nelson.com/science/9780176390785/student/attachments/ott/ani/school_flash.html?file=13_2_a_moving_magnet_in_a_coil

Drop Tower Rides Breaking systems use Lenz’s Law Frictional breaks wear quickly Electromagnetic breaking system is more reliable and automatic Each seat has a permanent magnet underneath The bottom 3rd of the tower has copper strips mounted vertically on the tower Carts fall past the copper strips, magnets induce an electric current in copper, the current produces a magnetic field which opposes that of the magnets on the seats and therefore stops the ride!

Homework Pg 591 #’s 1-6 (requires you to go back in the notes and read about the applications) Pg 594 #’s 1-4