Generating Electricity (Edexcel GCSE Physics): Revision Note

The Generator Effect

Higher Tier Only

• Electromagnetic (EM) induction is used to generate electricity

• EM induction is when:

  A voltage is induced in a conductor or a coil when it moves through a magnetic field or when a magnetic field changes through it

• This is done by the conductor or coil cutting through the magnetic field lines of the magnetic field

• This is often referred to as the generator effect and is the opposite to the motor effect

  • In the motor effect, there is already a current in the conductor which experiences a force

  • In the generator effect, there is no initial current in the conductor but one is induced (created) when it moves through a magnetic field

Generator Effect in the Laboratory

• A potential difference will be induced in the conductor if there is relative movement between the conductor and the magnetic field

• Moving the electrical conductor in a fixed magnetic field

  • When a conductor (such as a wire) is moved through a magnetic field, the wire cuts through the fields lines

  • This induces a potential difference in the wire

Moving an electrical conductor in a magnetic field to induce a potential difference

• Moving the magnetic field relative to a fixed conductor

  • As the magnet moved through the coil, the field lines cut through the turns on the coil

  • This induces a potential difference in the coil

When the magnet enters the coil, the field lines cut through the turns, inducing a potential difference

• A sensitive voltmeter can be used to measure the size of the induced potential difference

• If the conductor is part of a complete circuit then a current is induced in the conductor

  • This can be detected by an ammeter

Generator Effect in the Large-Scale Generation of Electrical Energy

• EM Induction can be used to generate electricity on a large scale by replacing the moving wire with a spinning coil

• An a.c (alternating current) generator looks very similar to a motor, but instead of connecting it to a power supply, a coil is spun to produce electricity

• As the coil rotates, it cuts through the field lines

• This induces a potential difference between the end of the coil, which also then creates a current

• The electricity produce is in the form of a.c which can be found in the mains supply of a building

• This is also called an alternator

A.C Generator