Magnetism and Electromagnetism

Question 1

What is a magnetic field?

Answer 1

A magnetic field is the region where magnets, magnetic materials and wires carrying currents experience a force acting on them.

Question 2

What type of force is magnetism?

Answer 2

Non-contact force - objects don’t need to be touching

Question 3

What are some magnetic materials?

Answer 3

• iron
• cobalt
• nickel
• steel

Question 4

What do magnetic field lines show?

Answer 4

• shows the direction of the magnetic force from one pole to the other that would act if another north pole was placed on that point
• lines have arrows - always point north to south
• the stronger the magnetic field, the closer together the lines
• as you get further away for the magnet the field becomes weaker

Question 5

Where is the magnetic field strongest?

Answer 5

At the north (seeking) and south (seeking) poles

Question 6

How would you draw out a magnetic field diagram?

Answer 6

You need: paper, a magnet, a plotting compass, pencil
1. Put the bar magnet on the paper and draw around it to mark it’s position
2. Place the plotting compass at a point on the bar magnet and mark the point on the paper
3. Mark where the plotting compass points to and shift the compass accordingly (back of arrow where front was before)
4. Repeat this process until you get a complete curve. Remember to mark what direction the compass pointed (so the field line pointed)
5. Repeat steps 2-4 multiple times with the plotting compass at different starting points around the bar magnet
6. You have a complete field diagram!

Question 7

What sort of force is there between a magnet and a magnetic material?

Answer 7

They always attract regardless of polarity of the magnet

Question 8

What is a permanent magnet?

Answer 8

A magnet/material that produces its own magnetic force

Question 9

What is an induced magnet?

Answer 9

• a magnetic material that becomes a magnet when placed in a magnetic field
• always causes a force of attraction
• quickly loses magnetism once removed form the magnetic field

Question 10

What happens if 2 permanent magnets are placed close together?

Answer 10

• like poles repel
• different/unlike poles attract

Question 11

What happens to the domains in an unmagnetised magnetic material when it is magnetised?

Answer 11

The domains go from pointing in random directions to all pointing in one direction (towards the magnet’s north pole)

Question 12

How does a compass work?

Answer 12

• inside it is a tiny bar magnet
• the north pole of it is attracted to any other nearby south poles of magnets
• the compass points in the direction of the magnetic field

Question 13

How do compasses show that the Earth’s core is magnetic?

Answer 13

When no other compasses are nearby, compasses always point north because the Earth generated its own magnetic field so the core must be magnetic