Magnetism

Magnets and Magnetic Fields Magnetic poles: one of two points, such as the ends of a magnet, that have opposing magnetic qualities. North or south poles 2 like poles repel each other. 2 unlike poles attract each other. Some materials can be made into permanent magnets. Iodestones

Magnets and Magnetic Fields Magnets exert magnetic forces on each other. Magnetic field: a region where a magnetic force can be detected. Magnets repel or attract each other because of the interaction of their magnetic forces. Magnets are sources of magnetic fields

Magnets and Magnetic Fields Magnetic field lines can be used to represent magnetic fields. Magnetic field lines always form closed loops. Compasses align with Earth’s magnetic field

Earth’s Magnetic Field Earth’s magnetic field runs from geographic south to geographic north. Magnetic north is different from geographic north. The source of Earth’s magnetism is not yet fully know.

Magnetism from Electric Current

Electromagnetism When a wire carries a strong, steady current, all the compass needles move to align with the magnetic field created by the electric current. Solenoids and bar magnets have similar magnetic fields. Solenoid: a coil of wire with an electric current in it.

Electromagnetism The strength of a solenoid can be increased. Electromagnet: a coil that has a soft iron core and that acts as a magnet when an electric current is in the coil Moving charge cause magnetism.

Electromagnetic Devise Electric motor: a device that converts electrical energy into mechanical energy. A motor can perform mechanical work when it is attached to an external devise. Galvanometers detects, measures, and determines currents in a circuit much like a voltmeter.

Right Hand Rule If you hold a wire in your right hand and point your thumb in the direction of the positive current, the direction that your fingers curl is the direction of the magnetic field. ** Never grasp or touch an insulated wire connected to a power source.

Electric Currents from Magnetism

Electromagnetic Induction Moving a magnet into and out of a coil of wire causes charges in the wire to move. Electromagnetic induction: the process of creating a current in a circuit by changing the magnetic field. Faraday’s Law: An electric current can be produced in a circuit by changing the magnetic field crossing the circuit.

Electromagnetic Induction Electromagnetic induction obeys conservation of energy. The magnetic force acts on moving electric charges. Generators convert mechanical energy into electrical energy. Alternating current (A/C): an electric current that changes direction at regular intervals. House current 110 V or 220 V Direct current (D/C): an electric current that goes in a straight line. Car current AA batteries

Electromagnetic Force Electricity and magnetism are two aspects of a single force, the electromagnetic force. EM waves are made up of oscillating electric and magnetic fields that are perpendicular to each other. EMP

Transformers Transformer: a device that increases or decreases the voltage or alternating current. Step-up transformer Step-down transformer In its simplest form, a transformer consists of two coils or wire wrapped around opposite sides of a closed iron loop. Transformers must obey the laws of conservation of energy. Transformers are used to transfer of electrical energy from high voltage to low voltage or low voltage to high voltage.