P4.5.2 - The A.C. Generator

Question 1

What is an A.C. generator? [2]

Answer 1

a device which converts energy from motion into an electrical output

Question 2

What does an alternating emf cause? [1]

Answer 2

an alternating current to flow

Question 3

What does a simple A.C. generator consist of? [3]

Answer 3

• a rotating coil of wire between the poles of a permanent magnet
• slip rings
• brushes

Question 4

What is the function of the permanent magnet? [1]

Answer 4

to provide a uniform magnetic field

Question 5

What is the function of a rotating coil? [2]

Answer 5

• to cut the magnetic field as it rotates
• allow an induced current to flow

Question 6

What is the function of slip rings? [2]

Answer 6

• to allow the alternating current to flow between the coil and external circuit

Question 7

What is the function of brushes? [2]

Answer 7

• to provide good electrical connection between the coil and the external circuit

Question 8

When is a maximum emf induced? [2]

Answer 8

• the position of the coil is horizontal
• the motion of the coil is perpendicular to the field

Question 9

When is no emf induced? [2]

Answer 9

• when the position of the coil is vertical
• when the motion of the coil is parallel to the field

Question 10

Why does the coil moving perpendicular to the field induce the emf? [1]

Answer 10

the greatest number of lines are cut when the coil is moving perpendicular to the field

Question 11

When the graph of an A.C. generator starts from a horizontal, how is the emf? [1]

Answer 11

emf is at a maximum

Question 12

When the graph of an A.C. generator starts from a vertical, how is the emf? [1]

Answer 12

emf is 0