Magnetism

Question 1

What is a:

Field line

Answer 1

A line of force that acts on magnetic materials which shows the direction a North pole would move

Question 2

Why is it that:

Not all metals are magnets

Answer 2

Each force of each domain can end up pointing in random orientations which usually end up cancelling each other out leading to an overall magnetic field of 0

Question 3

How can:

A ferrous material be magnetized

Answer 3

• Passing a strong current through it
• stroking with a magnet
• Letting it cool very slowly

Question 4

Can:

Non-ferrous metals be magnetized

Answer 4

Yes - by passing a current through the metal
However, as soon as the current is removed it will lose its magnetism

magnetically hard does not lose magnetism easily
soft materials do

Question 5

Rules when drawing field lines

Answer 5

• No loose ends
• No lines touching or crossing
• Arrows point from North to South
• More field line density = more field line strength
• when 2 poles repel, no lines in the middle

Question 6

How to:

Demagnetize a permanent magnet

Answer 6

• Hit with hammer
• heat the magnet

Question 7

What is:

Right hand Grip rule

Answer 7

Thumb → current direction
knuckles to fingertips → North (in a circle)
Shows where a north pole would move

Question 8

How can the:

Right hand grip rule be used for Solenoid

Answer 8

1. Grab soloneid with middle fingers
2. make sure hand is in the direction of the flow of current
3. thumb → force

Question 9

What is:

Flemming’s left hand rule

Answer 9

• Thumb → force
• index → field line
• middle → current

FBI
All quantities are at 90°

Question 10

What is the:

Motor effect

(General answer)

Answer 10

1. Current flows in the wire/coil
2. causes a magnetic field across the wire
3. this fields interacts with permanent magnet
4. this causes a force on the wire
5. direction of the force can be found with FLHR

Question 11

How can:

The motor effect be sped up?

Answer 11

• Increase current
• Increase magnetic field strengh by using stronger permanent magnets
• put magnets close together
• more length of wire

Question 12

How do:

Speakers work

Answer 12

• Speakers create sound by vibrating
• Change in current direction causes vibrations
• A.C. current then must be used

(For model answer, use motor effect model answer aswell)

Question 13

INTO OUT SIGNS

Answer 13

Into the paper -> cross
Out of the paper -> Dot

Question 14

How to:

Find the magnetic field of a magnet

Answer 14

1. Place a card above the wire
2. Sprinkle a lot of magnetic iron filings on the page
3. Gently tap page so that iron filings move around a bit
4. Use a compass to find the direction of North.