17. Electromagnetic Induction

Question 1

What happens when a conductor is moved across a magnetic field? (electromagnetic induction)

Answer 1

• conductor/wire cuts through magnetic field lines
• potential difference is induced
• if wire is part of complete circuit a current will flow
• wire and magnetic field must move perpendicular to each other (no field lines are cut if move parallel to each other, no potential difference is therefore induced)

Question 2

How can a larger potential difference be induced?

Answer 2

1. More turns in coil
2. Stronger magnetic field
3. Faster movement

Question 3

How can the direction of the current be changed?

Answer 3

1. Changing direction of magnetic field
2. Changing direction of movement

Question 4

What is a generator?

Answer 4

Device that electrically transfers kinetic store of generator into other stores (opposite of electric motor)
Produce electricity

Question 5

Describe how an AC generator works

Answer 5

• coil of wire is spun in magnetic field
• coil cuts through magnetic field lines so potential difference is induced
• as coil spins each part of wire sometimes movs up and sometimes down
• because it changes direction current that is induced is an alternating current (changes direction)

Question 6

How does a DC generator (dynamo) generate a direct current?

Answer 6

• split ring commutator converts alternating current into direct current

Question 7

How does a bike dynamo work?

Answer 7

• spins magnet in a coil as wheels move instead of coil of wire
• magnetic field lines cut through sides of coil inducing potential difference in coil
• magnetic field constantly changing direction as it rotates, output current is also alternating - so unlike normals dynamos it produces a ac not dc current

Question 8

What do the slip rings do in an AC generator?

Answer 8

• connect coil to brushes, maintains a/c inside coil to a/c in outer circuit