Magnetism Electromagnetism Physics Magnetism A permanent magnet has

Magnetism & Electromagnetism Physics

Magnetism • A permanent magnet has an invisible force field around it. • This force field can attract or repel other magnets. • Magnets can also attract materials made from ferrous metals. • Examples of ferrous metals are – Iron Nickel & Cobalt

Magnetic Field pattern • The magnetic field around a bar magnet can be seen by sprinkling iron filings around a bar magnet

What things are attracted to a magnet Attracted Not Attracted

Magnets in action • Magnetic levitation • Magnetic fluid • Magnets – National Geographic • Maglev train - Japan

Making an electromagnet • Wrap a long piece of wire around an iron nail • Connect the bare ends to a battery or a lab pack. • Dip the end of the nail in a tub of paper clips. • Switch on and off to turn the electromagnet on and off.

Electromagnet investigation • What affects the strength of an electromagnet • Voltage • Length of coil • Number of turns on the coil • Type of core Using the coils available try to find out how to make the strongest electromagnet

Uses of Electromagnets • Electromagnets have many uses. Here are just a few: device Electric bell Solenoid (electronic plunger) Relay Electric motor Danger with magnets - watch uses Door bell, school bell Car locks Remote switch Fan, power tools, electric car

Electric bell • When the switch is pressed the coil becomes a magnet. • This attracts the iron striker which hits the bell • The contact is opened and the magnet is turned off. • The striker then moves back and the contacts touch again. • This repeats for as long as the switch is pressed

Solenoid – electronic lock When a current flows the magnetic plunger is pulled into the coil. When the electricity is turned off or it flows in the opposite direction, the plunger moves back out.

Relay • A very low powered circuit can turn on a high powered circuit. • These are used in stage lighting rigs and stadium floodlights.

Electric motor • A current is passed to the coil through the brushes. • The current makes the coil an electromagnet • The coil then interacts with the stationary magnets. • It rotates.

Build an electric motor Watch the demo…then build your own.

Uses of electromagnets