Magnetism and Electromagnetism

What effect does this demonstrate?

Generator Effect

Explain why current was detected when the wire was moved upwards?

• Wire cuts through a magnetic field

• A potential difference is induced across the wire

• As it was part of complete circuit

Explain why the sound waves have an effect on the electric circuit

• Pressure variations in the sound waves cause the diagphram to vibrate

• Diagphram causes the coil to vibrate

• Inducing an alternating current in the circuit

What material is used for the core? Why?

• Iron

• It is easily magnetised

Explain why a direct current is induced in the coil

• The coil cuts through the magnetic field

• A potential difference is induced across the coil

• There is a complete circuit, so a current is induced

• Each half-revolution, the two ends of the coil swap from one brush to another

• So the direction of current does not reverse at every half rotation

• After disconnection there is no induced current

• So no magnetic field to oppose movement of the coil

Identify the labelled parts

A - Primary Coil

B - Secondary Coil

C - Iron Core

An input pd causes an alternating current.

Explain why there is an alternating current in the output when the transformer is connected to a circuit.

• A changing magnetic field around the primary coil

• Creates a magnetic field which changes direction in the core

• Induces an alternating potential difference across the secondary coil

Which letter shows where the magnetic field is strongest?

A

A - Decrease the distance between the electromagnet and the iron arm