Topic 6: Generators and moters

Question 1

What is a generator?

Answer 1

A device that converts mechanical energy into electricity using the relationship between electricity and magnetism

Question 2

What is an electromagnet?

Answer 2

A magnetic current created by the flow of electricity

Question 3

How can you increase the strength of the current?

Answer 3

Increase the size of the core
Increase the strength of the current
Increase the number of coils

Question 4

What happens to an electromagnet when the current in reversed?

Answer 4

The polarity of the magnet is reversed

Question 5

How does an AC generator use magnetism to create an electric current?

Answer 5

-An AC generator consists of a coil wire that rotates
inside a stationary magnet
- The coil is rotated by an external power source
(i.e., wind, steam, water), causing electrons to
move along the wire in one direction
- After one half-revolution of the wire loop, each
side of the coil passes near the opposite pole of
the magnet, causing the electrons to move in the
opposite direction
- Thus called “alternating current” because electron
flow is constantly changing direction

Question 6

How does a DC generator work?

Answer 6

• Consists of a rotating loop of a wire(known as an armature) connected to the outside circuit by a split ring (AKA halfring) commutator
• The split ring commutator essentially acts to make electrons flow in one direction.Split metal rings are connected by small brushes, which permit electron flow through the armature
• When the armature and commutator rotate, the brushes are no longer in contact with the split metal rings, causing a momentary pause in current flow
• As the armature continues to rotate and thebrushes come back into contact with the commutator the current resumes in the opposite direction; however, the connection through the commutator has also been reversed, so the current continues through the load in a constant direction

Question 7

What does a DC generator consist of?

Answer 7

• Armature –Rotating loop of wire (usually coiled)
• Split-ring commutator –acts to make electrons flow in one direction
• Brushes –Connected to the split metal, when not touching ring there is a pause in current
• Permanent magnet –magnet does not move

Question 8

What are the pros/cons of ac generators?

Answer 8

Pros
- Good at carrying power over great distances

Question 9

Who discovered the link between electricity and magnetism? How?

Answer 9

Hans Christian Oersted, by placing a magnetic compass needle near an electric wire