Generating

Question 1

How is a voltage induced onto a wire?

Answer 1

• When a wire is held stationary between the poles of a magnet, there is no current in the wire.
• If the wire is moved upwards, a voltage is induced in the wire and a current passes. The same thing happens if the magnet is moved downwards.
• When the wire moves downwards or the magnet moves up, the induced voltage and current is in the opposite direction
• Reversing the direction of the magnetic field also reverse the induced voltage and current direction.

Question 2

When is a voltage induced?

Answer 2

A voltage is induced whenever a magnetic field changes.

Question 3

What does the size of the induced voltage depend on?

Answer 3

• The size of the induced voltage depends on the rate at which the magnetic field changes:
  
  • If the wire is moved slowly voltage is low.
  • If the wire is moved quickly voltage is high.

Question 4

How is the magnetic field inside the coil produced in a power station?

Answer 4

By electromagnets. The electromagnet is made from the coils of wire (rotor wire) which are turned by the turbine.

Question 5

Where is the AC current produced?

Answer 5

An AC current is produced in the stator coil which surrounds the rotor coil.

Question 6

What happens when the speed of rotation in the electromagnet increases?

Answer 6

• Increasing the speed of rotation of the electromagnet increases both the current induced in the stator coil and the frequency of the voltage generated.

Question 7

What happens when the number of turns on the electromagnet increases?

Answer 7

Increasing the number of turns on the electromagnet increases the magnetic field and therefore a larger voltage is induced in the stator coil.

Question 8

What is another way to generate electricity?

Answer 8

Some AC generators do have a rotating coil between the poles of a magnet.

Question 9

Why is the output of the a generator AC?

Answer 9

As the coil rotates, the direction of the current in the coil reverse every half turn.

Question 10

What is the purpose of slip rings?

Answer 10

Slip rings are connected to the ends of the coil to allow the coil to spin without winding the wire around itself.

Question 11

What are brushes?

Answer 11

The brushes are contacts that touch the slip rings and complete the circuit.