Magnetism and Electromagnetism

A magnet is any material that attracts iron and materials that contain iron. Magnets will attract or repel other magnets. In addition, one end of a magnet will always point North when allowed to swing freely.
Any magnet, no matter what its size or shape, has two ends. Each one is called a magnetic pole.
Magnetic poles that are unalike attract each other, and magnetic poles that are alike repel each other.
A magnetic force is produced when magnetic poles come near each other and interact. Any material that exerts a magnetic field is a magnet.
The area of magnetic force around a magnet is known as its magnetic field. Magnetic fields likes spread out from one pole, curve around the magnet, and return to the other pole.
Earth has a magnetic field around it and two magnetic poles.

Electromagnetism

The relationship between electricity and magnetism is called electromagnetism. An electric current creates a magnetic field.
The magnetic field produced by a current has a strength and a direction. This field can be turned on or of, have its direction reversed, or have its strength changed.
A coil of wire with a current is a solenoid. The two ends of the solenoid act like the poles of a magnet. The North and South poles change when the direction of the current changes.
Both solenoids and electromagnets use electric current and coiled wires to produce strong magnetic fields.
If you place a material with strong magnetic properties inside a solenoid, the strength of the magnetic field increases. A solenoid with a ferromagnetic core is called an electromagnet.
You can increase the strength of an electromagnet in four ways, first you can increase the current in the solenoid. Second, you can add more loops of wire to the solenoid. Third, you can wind the coils of the solenoid closer. Finally, you can use a material that is more magnetic than iron for a core.

Electrical energy and Mechanical energy

The energy associated with electric currents is called electrical energy. The energy an object had due to it’s movement or position is called mechanical energy.
A galvanometer is a device that measures small currents. An electric current turns the pointer of a galvanometer.
When a wire with a current is placed in a magnetic field, electrical energy is transformed into mechanical energy.
An electric motor is a device that uses an electrical current to turn an axle. Electric motors turn electrical energy into mechanical energy.
An electric current is induced in a conductor when the conductor moves through a magnetic field. Generating electric current from the motion of a conductor through a magnetic field is called electromagnetic induction. Current that is generated this way is called induced current.
Moving the coil or the magnet induces the current without any voltage source. The direction of an induced current depends on the direction the coil or magnet moves.
A current with charges that flow in one direction is called direct current. A battery produces direct current when a battery is placed in a circuit and charges flow in one direction.
A consistently reversing current is called alternating current. You could induce alternating current by moving either the coil or the magnet up and down repeatedly.
Alternating current has a major advantage over direct current. An alternating current can be easily raised or lowered.
A generator uses motion in a magnetic field to produce current.

# Transformers

A transformer is a device that increases or decreases voltage. A transformer consists of two separate coils of insulated wire wrapped around an iron core. The primary coil is connected to a circuit with a voltage source and alternating current. The secondary coil is connected to a separate circuit that does not contain a voltage source.
The changing current in the primary coil produces a changing magnetic field. This changing magnetic field induces current in the secondary coil.
The change in voltage from the primary coil to the secondary coil depends on the number of loops in each coil.
Step-up transformers increase voltage. The primary coil has fewer loops.
Step-down transformers decrease voltage. The primary coil has more loops.