Do now: Finish these sentences 1)Electromagnetic induction is... 2)Electromagnetic induction is used for... Paraire, 4 Hakihea 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:

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

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!

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