Generators

• To explain how a generator works to produce electric current.

• To explain the difference between alternating and direct current.

Producing Electricity• Electricity is produced by generators.

Key Terms You need to Understand!

• Electricity is the flow of charged particles called electrons.

• Current is the rate of flow of electrons.

• Voltage is the push of electrons – it measures the amount of energy at a given point.

How a generator works

• You need three things for a generator to work:–A magnet–Coils of wire–Movement

Producing electricity…

• Moving a piece of wire in a magnetic field causes an electric current to flow through the wire.

• This process is called electromagnetic induction.

• Current produced this way is called an induced current.

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permanent magnet

coil of insulated wire

galvanometer

Electromagnetic InductionWhen a magnetic field ‘cuts’ though a conductor, a voltage is induced, resulting in a flow of electric current. This is called electromagnetic induction.When the magnet moves out of the coil, the polarity of the induced voltage reverses and the current flows in the opposite direction.When the magnet stops moving there is no induced voltage and no current flowsIf the number of turns in the coil is increases, the size of the induced voltage increases, resulting in a larger current.If a stronger magnet is used, the size of the induced voltage increases, resulting in a larger current.This can be investigated using the following pieces of equipment:A galvanometer is an instrument for measuring, or detecting, very small currents.If the magnet moves faster, the size of the induced voltage increases, resulting in a larger current.The size of the induced voltage can be increased by:

● increasing the strength of the magnet● increasing the number of turns in a coil● increasing the speed of the magnet

When a magnet moves into a coil of wire, a voltage is induced and current flows in one direction.As the magnet moves in an out of the coil, a current is induced that periodically changes direction. This is called an alternating current.

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You can get the same effect by moving the wire and keeping the magnet still.

How current can be increased…

• Adding more turns on a coil of wire

• Using stronger magnets

• Moving the wire faster

Direction of current

• The direction of current can be changed by changing the direction…

–Of the movement of wire–Of the magnetic field

DynamosA dynamo is a particular type of

generator which is often used on bikes to power lights. Here the magnet is

rotated instead of the coil. They dynamo is attached to a wheel so as

you turn the wheels, your turning inside the dynamo.

Dynamos• Current produced in

a simple dynamo can flow in two ways, if it flows in the same direction and is called direct current (DC).

• If it flows and keeps changing direction it is called alternating current(AC).

Generators• In a generator

wire goes up and down within the magnetic field.

• This causes the induced current to change direction.

• Current that changes direction like this is called alternating current (AC).

Generators in Power Stations

• Generators in power stations produce a lot of energy and need to induce a strong voltage.

• To do this, electromagnets are used instead of permanent magnets, which are expensive.

• Electromagnets are stronger magnets which can be switched on and off.

Question

1. Put more turns of wire on the coil, spin the coil faster, use stronger magnets

2. They need to generate large currents, so they need powerful magnets and electromagnets are stronger than permanent magnets.