magnetism and electromagnetism

Question 1

What are magnetic field lines?

Answer 1

Lines of force, showing size and direction of magnetic fields. Always point from north to south

Question 2

How would you investigate the magnetic field pattern for a permanent bar magnet?

Answer 2

1. Use multiple compasses to see the magnetic field lines: north points of compasses will all be attracted to south point of magnet 2. Sprinkle iron filings on paper and put magnet underneath paper - will move to show magnetic field lines

Question 3

How would you use two permanent magnets to produce a uniform magnetic field?

Answer 3

Place north and south poles near to each other. Lines of force are straight between the poles, curved at edges

Question 4

Describe the magnetic field produced by a current-carrying wire

Answer 4

1. A current-carrying wire creates a magnetic field
2. The larger the current, the stronger the magnetic field
3. The direction of the magnetic field depends on the direction of the current

Question 5

What happens when a current-carrying wire is put into a magnetic field?

Answer 5

Current-carrying wire creates its own magnetic field. The two magnetic fields affect one another, producing a force on the wire which causes it to move

Question 6

Describe Fleming’s Left Hand Rule

Answer 6

First finger = field, seCond finger = current, thuMb = motion (of wire). Motion shows you direction of force

Question 7

What happens if you change the magnitude or direction of the current or magnetic field?

Answer 7

1. Size of force increases if current or magnetic field is increased
2. Direction of force reverses if current or magnetic field is reversed

Question 8

Give 4 ways to speed up a simple electric motor

Answer 8

1. Increase the current 2. More turns on the coil. 3. Stronger magnetic field 4. Use a soft iron core in the coil

Question 9

Why do you need a split ring commutator?

Answer 9

Swaps the contacts every half turn to keep the motor rotating in the same direction

Question 10

How can you reverse the direction of the motor?

Answer 10

1. Reverse direction of current or 2. Swap magnetic poles over

Question 11

How does the motor effect make a loudspeaker work?

Answer 11

When ac current flows through coil of wire it is surrounded by permanent magnet so experiences a force. This makes the cone of the loudspeaker vibrate, which creates sounds.

Question 12

What is electromagnetic induction?

Answer 12

The creation of a voltage in a wire which is experiencing a change in magnetic field

Question 13

What is the dynamo effect?

Answer 13

Using electromagnetic induction to transform kinetic energy into electrical energy

Question 14

How do you increase the voltage in electromagnetic induction?

Answer 14

1. Use a stronger magnet 2. Increase the number of turns on the coil 3. Increase the speed of movement