Electromagnetism

Induced voltage

  • A voltage will be induced (generated) in a wire when the wire is moved between the poles of a magnet.
  • If the wire forms part of a complete circuit, this induced voltage will cause a current.
  • The induced voltage can be made greater if the wire is formed into a coil.

Look at the meter readings in the following images.

Step one

Magnet with a wire wrapped around it. The meter reading is zero Magnet with a wire wrapped around it. The meter reading is zero

Step two

Magnet moves from north to south through wire, meter reading is now positiveMagnet moves from north to south through wire, meter reading is now positive

Step three

Wire wrapped around all of magnet, meter reading is zeroWire wrapped around all of magnet, meter reading is zero

Step four

Magnet moves from south to north through wire, meter reading is now negativeMagnet moves from south to north through wire, meter reading is now negative

The voltage is induced and so the current is generated, only when the magnet and the wire (coil) move relative to each other. This is because a conductor must cut across magnetic field lines for a voltage to be induced.

Move on to Test
next