Electromagnetic induction

What is induced when a conductor or a coil moves through a magnetic field or when the magnetic field changes through it?

A voltage

What factors affect the size of the induced voltage of the conductor or coil when it moves through a magnetic field or a magnetic field changes through it?

• The speed at which the conductor or coil is moved through the magnetic field

• The speed at which the magnet is moved through the coil

• The strength of the magnetic field used

• The number of loops of coil

• The size of the loops of coil

Describe the generation of electricity by the rotation of a magnet within a coil of wire and the coil of wire within a magnetic field.

The rotation of the magnet inside a coil of wire or by rotating a coil of wire inside a magnetic field induces a potential difference (voltage) between the ends of the coil, causing the current to flow, generating electricity.

What factors affect the size of the induced voltage when rotating a magnet within a coil of wire and the coil of wire within a magnetic field?

• Strength of magnetic field

• Size of coil

• Number of loops of coil

• Speed of magnet

• Speed of rotation of coil of wire

What is the purpose of a transformer?

It is used to increase or decrease the voltage of of an alternating current by having different numbers of turns on the input and output sides.

How does a transformer work?

• When supplied with an alternating current, the primary coil will generate an alternating magnetic field

• Which then induces an alternating magnetic field in the iron core

• Which then induces an alternating voltage in the secondary coil

• And if the circuit is complete, will lead to an alternating current

Describe the structure of a transformer.

• Iron core (magnetic field)

• a.c. input

• a.c. output

• primary coil

• secondary coil

What is a step-up transformer?

It increases the voltage and decreases the current

Explain the use of a step-up transformer in the large scale generation and transmission of electrical energy.

It could be used as electricity leaves a power station and enters the national grid

Why is it important to use a step-up transformer before electricity is transmitted from a power station to the national grid?

It is important to have a high voltage and low current in order to minimise energy loss during transmission as a high current would heat the wires, causing energy loss via heat

What is a step-down transformer?

It decreases the voltage and increases the current

Explain the use of a step-down transformer in the large scale generation and transmission of electrical energy.

It could be used before electricity enters a home, to ensure the voltage is low enough

State the equation linking the relationship between input (primary), output (secondary) voltage and turns (primary, secondary)

input (primary) voltage / output (secondary) voltage = primary turns / secondary turns

State the equation linking input and output power for 100% efficiency

input power = output power

V_pI_p = V_sI_s

V = voltage

I = current

p = primary

s = secondary