P1aL12 Generating Electricity

Key Words

Ammeter - instrument to measure current

Armature - central part of a motor that moves when an electric current flows.

Dynamo - a small generator.

Electrical Energy - energy transfer with electrons.

Electric Current - the flow of electrons

Electricity Generator - a machine that converts kinetic energy from an engine into electricity.

Electric Motor - a machine that converts electrical energy into kinetic energy

Electromagnet - a magnet that is magnetised only when an electric current flows.

Kinetic energy - energy of movement

Magnet - a material that attracts certain magnetic materials to itself.

Movement - when something moves (really?).

Grade E

Electric motors turn electrical energy into kinetic energy.

This little motor will generate an electric current if we spin it.  It would give a reading on a sensitive ammeter.  The faster we turn it, the bigger the reading.  If we connected it to a bulb, the bulb would glow brighter.

The generator is a motor in reverse.  It turns kinetic energy into electrical energy.

Small generators are often called dynamos.

Grade C

Wherever there is an electric current, there is always a magnetic effect (a magnetic field).  A current carrying coil of wire will move a magnet.  Or a magnet will move a current carrying coil.

A moving magnetic field will make an electric current is it passes a coil.  It doesn't matter if the magnet is moving past the coil, or the coil passes the magnet.  A current is made which passes to a circuit.  The direction of the current will reverse if a south pole passes it instead of a north pole.  Or if the north pole is moved in the opposite direction.

We can use this effect in the electric motor.  The picture shows a small motor under test:

The motor has an armature which is a coil of wire that spins when a current goes through it.  In the diagram of the simple motor below, the side next to the North pole goes up, while the side next to the south poles moves down.  This gives a turning effect.

A motor turns electrical energy into kinetic energy.  Running the motor in reverse turns the kinetic energy into electrical; it's a generator.

Grade A

The biggest turning effect happens when the armature is in the position above.  When it's in the vertical position there is no turning effect at all and the motor relies on the momentum of the coil to keep it turning.  This does not make for an efficient motor, and if the motor is under load, it will stall.

Practical motors have a number of coils of wire in the armature.  The little motor at the top of the page has three.

The picture here shows the armature of a traction motor used in an electric locomotive.  There are two hundred coils.