Generator effect

how do wind turbines work?

• wind turns turbine

• turbine turns generator

• generates electricity

electromagnetic induction

if we place a conductor ( not carrying a current) inside a magnetic field and we make it move the we will produce a current

how does electromagnetic induction work?

• a potential difference is induced across the ends of the conductor when it is moved relative to the magnetic field

• also happens if the magnetic field around the conductor is changed

• conductor is cutting/crossing magnetic field lines

generator effect

conductor that is part of a complete circuit moves through a magnetic field, cutting magnetic field lines → current will be induced as potential difference has been induced

4 ways to increase current

• increase strength of magnet ( stronger magnet as size doesn’t affect strength)

• increase number of turns of coil

• moving magnet fasterhave magnet closer to coils

How can a solenoid and magnet be used to generate a current?

• When a magnet is moved into or out of a solenoid, the magnetic field through the coil changes, which induces a current.

• A current is only produced while the magnet is moving.

• The magnetic field generated in the solenoid always acts to oppose the change

• When the magnet is pushed into the coil, the solenoid produces a magnetic field that repels the magnet, opposing its entry.

• When the magnet is pulled out, the solenoid produces a magnetic field that attracts the magnet, opposing it leaving (trying to pull it back in).

• This opposition to the motion is what shows that a current has been induced, and reversing the motion reverses the current direction.

How can we know which direction a current is by looking at a solenoid?

• south = clockwise

• north = anticlockwise

How can we tell which direction the current moves in a solenoid?

• the induced magnetic field opposes the change.

• we’re pushing the south seeking pole into the coil

• the left end of the solenoid must be at the south pole (its repelling the south seeking pole of the magnet)

• if its southpole then the current at the left must be clockwise

How does moving a magnet in a coil change current?

• When we move a magnet into a coil of wire, a current is generated but only while it is moving.

• If you pull the magnet out, the current flows in the opposite direction.

How is the generator effect used to induce a current?

• The generator effect is when a moving conductor in a magnetic field produces a current.

• When a coil moves between the poles of a magnet, it cuts across magnetic field lines.

• This induces a potential difference (voltage) across the coil.

• If the circuit is complete, a current flows.

How does a microphone work?

• A microphone has a coil attached to a flexible diaphragm inside a cylindrical magnet.

• Sound waves cause the diaphragm to vibrate.

• This moves the coil in a magnetic field.

• This induces an alternating potential difference (a.c.).

• The frequency of the a.c. is the same as the sound waves.