GCSE Physics Revision: Magnetism and Electromagnetism notes

Magnetism

Magnetism is the property of certain materials to attract or repel each other. There are two types of magnets:

• Permanent magnets, which retain their magnetism even when not in the presence of a magnetic field.
• Temporary magnets, which only exhibit magnetism when in the presence of a magnetic field.

Some common magnetic materials include iron, cobalt, and nickel.

Electromagnetism

Electromagnetism is the interaction of electric fields and magnetic fields. When an electric current flows through a wire, it creates a magnetic field around the wire. This is known as an electromagnet.

The strength of an electromagnet can be increased by increasing the number of turns in the wire, increasing the current flowing through the wire, or by using a ferromagnetic core inside the coil.

The Motor Effect

The motor effect is the phenomenon where a current-carrying wire experiences a force when placed in a magnetic field. This force is perpendicular to both the direction of the current and the direction of the magnetic field.

The magnitude of the force is given by the equation F = BIL, where F is the force, B is the magnetic field strength, I is the current, and L is the length of the wire in the magnetic field.

Motors

A motor is a device that converts electrical energy into mechanical energy. The most common type of motor is the electric motor, which uses the motor effect to produce a rotating motion.

The basic components of an electric motor include a rotor (the rotating part), a stator (the stationary part), and a commutator (which allows the current to flow in the correct direction to produce continuous rotation).

Generators and Dynamos

A generator is a device that converts mechanical energy into electrical energy. The basic components of a generator include a rotor (which rotates to produce a changing magnetic field) and a stator (which contains the wire coils that generate the electrical energy).

A dynamo is a type of generator that uses a commutator to produce a DC (direct current) output.

Transformers

A transformer is a device that is used to change the voltage of an alternating current (AC) electrical supply. Transformers consist of two coils of wire (the primary coil and the secondary coil) that are wrapped around a common iron core.

The voltage output of the transformer is determined by the ratio of the number of turns in the primary coil to the number of turns in the secondary coil.