Do now: Finish these sentences 1)Electromagnetic induction is... 2)Electromagnetic induction is used for... Hātarei, 24 Whiringa-ā-nuku 2015 The conversion of mechanical energy to electrical energy A voltage that is produced across a wire when it moves relative to a magnetic field – a current can flow if the circuit is complete Generating electricity For example: a bicycle dynamo a car generator the turbines of a hydro electric power station

x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x + Force on a moving charge:

Right Hand Slap Rule v=direction of wire movement v=direction of wire movement B=direction of magnetic field lines B=direction of magnetic field lines F= force on a positive charge (i.e. direction of current flow) F= force on a positive charge (i.e. direction of current flow)

x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x Force on charges in a moving wire:

Ammeter Electromagnetic induction

Scan figs 15.2, 15.4, 15.5 to show current flipping. Explain no current in side wires because perpenducular. Lenz law is like men and women: women run when men chase them, but when the man tries to leave, she starts chasing him!

V = BvL V = induced voltage B = magnetic field strength v = speed of movement across B L = length of wire in B Calculate the size of V and the direction of the induced current as the loop : enters the magnetic field is completely in the field leaves the field V = 0.80 x 0.10 x 0.50 = 0.040V, anticlockwise V = 0 (AB cancels BC) V = 0.040V, clockwise

Lenz’s Law “The coil tries to oppose the force of the magnet” The coil does not have the opposite pole to the magnet!

Try Activity 15A - just Question 1! Then go back and read pages