The link between electricity & magnetism N S When a wire moves through a magnetic field a voltage is produced N Moving a magnet moves through a coil of wire will induce a current Moving the magnet faster increases the current. Moving the magnet out makes the magnet go in the opposite direction Putting the south pole first also changes the directions of the current

Currents and magnetic fields All currents produce a magnetic field The magnetic field along a current in a wire looks like….. A series of circles running perpendicular to the wire The magnetic field around a coil or solenoid looks like….. Coil of wire Iron core The shape of a bar magnets field

N S If a wire with a current flowing goes through a magnetic field it is forced to move (up or down). If you coil a wire it will rotate. This is how motors work 1. A current goes through the wire 2. The coil of wire is in a magnetic field 3. Which makes it turn How can you make it turn faster? Larger current Stronger magnets More turns of wire How can you make it turn the other way? Reverse the current Reverse the magnetic field Coil of wire Commutator: Keeps the motor turning in the same direction

To improve the efficiency of commercial motors the coil is cylindrical The motor only turns efficiently if the coil is 90 degrees to the magnetic field If the magnets have curved faces and the coil is also cylindrical then it will always be 90 degrees to the magnet We say it has a radial field

The dynamo N S Iron core Coil of wire 1.Magnet rotates 2. Induces a changing magnetic field in the core 3. The magnetic field induces an a.c current in the coil Spinning the magnet faster increases….the frequency and the voltage Increasing the number of turns increases….the voltage

The A.C. generator 1The axle is made to turn 2The coil spins in a magnetic field 3A current is induced Each slip ring is connected to a different end of the coil. This produces…….. An alternating current (a.c)