Magnetism Unit Summary

Electromagnetic induction is when a change in the magnetic field of a wire loop induces voltage which causes current. This can be seen in traffic lights, airport metal detectors, credit card machines, and transformers. The magnetic field changes when a magnet moves through a coil of wire or vice versa.
In traffic lights for example, the metal of the car moves over coils of wire in the road which changes the wires magnetic field. This induces voltage which causes current. The current sends a signal to the light for it to turn green when there is a car there.
Transformers have no magnet but are made up of two current carrying wires next to each other. They are used to increase or decrease voltage and can be seen in most appliances such as refrigerators, hair dryers, computer chargers, washing machines, etc. The magnetic field of the primary wire changes because of its alternating current which causes a change in the magnetic field of the secondary which induces voltage which causes current.
Generators convert the mechanical energy of a spin into electric energy which is a change in current. Generators can be found in things like wind turbines or hydroelectric dams. In the case of the wind turbine, the wind spins the blades, the blades move the magnets through the wire or vice versa which changes the wires magnetic field which induces voltage which causes current.

Forces on Charged Particles are important when it comes to cosmic rays and motors. When cosmic rays, or charged particles approach the earth at its equator, the charges are moving perpendicularly to the earths magnetic field lines so they feel a force and do not enter. However if the particles approach the earth towards the geographic north, the charges are moving parallel with the earths magnetic field lines so they do not feel a force and they enter. This is what causes the northern lights and why the northern lights are only seen at the north and south of the earth. The geographic north and south are opposite from the magnetic north and south because of these magnetic field lines.
Motors are made of coils of wire and magnets and are the opposites of generators. They convert electrical energy from a battery or other power source to mechanical energy like the spinning of a wire. The current carrying wire feels a force in the magnetic field because of the magnet and this causes the torque of the wire.

Magnetic Fields are essential in understanding magnets and magnetism. The source of magnetism is moving charges. When charges move in a wire there is current. When something is magnetized, the domains of the object all line up with the magnetic field lines which go from south to north. Like poles repeal and opposites attract because the magnetic field lines need to be parallel in order for the poles to attract. An object can be magnetized if it is brought into contact with a magnetic field causing the domains to line up. Compasses are simply magnets that are free to move to line up with the earths magnetic field.