8-2 Electricity & Magnetism

1. Discoveries Electric currents produce a (circular) magnetic field around the wire. The direction of the magnetic field changes with the direction of the current. The strength of the magnetic field depends upon the amount of current flowing in the wire.

2. Electromagnet Temporary magnet formed by placing iron in a current carrying coil of wire. The more layers of coil, the stronger the magnet. The higher the current, the stronger the magnet. Maintains all the properties of a “magnet”. Changes electric energy to mechanical energy.

3. Galvanometers Devices which use an electromagnet to measure electric current. Temporary magnet (needle) is suspended so that it can rotate along the field lines of the permanent magnet.

4. Electric Motor A device that changes electrical energy into mechanical energy. Contains an electromagnet that is free to rotate between the poles of a permanent fixed magnet. Magnetic field continues – current is reversed which keeps the coil rotating to line up the opposite poles.