Magnetism

Question 1

What are magnets comprised of and what the rules regarding attraction and repulsion?

Answer 1

• A magnetised object made of a magnetic material known as a magnet will have two ends known as poles which will be the north and the south pole
• When two magnets are held in close proximity to eachother, there will be an attactive or repulsive force depending on their positioning
• The north and south poles will be attracted to eachother, while the north and north and the south and south poles will repel eachother

Magnets are specifically magnetised objects with a north and south pole which attract and repel whereas magnetic materials are simply materials which can be made magnetic

Question 2

What are magnetically hard materials?

Answer 2

• They are materials which are difficult to magnetise, but once magnetised stay this way permanently
• Permanent magnets are made out of magnetically hard materials

An example is steel

Question 3

What are magnetically soft materials?

Answer 3

• They are materials which are easy to magnetise but will also easily lose their magnetism
• Temporary magnets, namely electromagnets, are made of magnetically soft materials so they can be made magnetic or non-magnetic when required

Question 4

What is a magnetic field?

Answer 4

The region around a magnet where a force acts on another magnet or magnetic material

Question 5

What do magnetic field lines represent and how do they do this?

Answer 5

• They represent the strength and direction of a magnetic field
• The direction is represented by arrows on the line
• The strength is represented by the spacing of the magnetic field lines - the closer together they are the stronger the magnetic field

Question 6

What are two rules regarding magnetic field lines?

Answer 6

• They always go from north to south (indicated by the arrows)
• They never cross or touch eachother

Question 7

What does the magnetic field of a bar magnet look like?

Answer 7

• The field is strongest at the poles so this is where the lines are the closest - as the distance from the poles increase, so will the distance between the field lines
• The lines will go from north to south
• They will go in all directions in order to get from north to south, as seen below

Question 8

How can a uniform magnetic field be formed?

Answer 8

• Place two bar magnets with the north and south poles facing each other a few centimeters apart
• A uniform magnetic pole will be produced in the gap between the opposite poles
• A uniform magnetic field has the same strength and direction at all points

Question 9

How can you test whether something is a magnet or just a magnetic material?

Answer 9

• If it is a magnet, then it will be able to repel and attract known magnets as it has two different poles
• If it is a magnetic material, it will be attracted to all known magnets regardless of the poles (because the end of the material closest to the magnet will temporarily have the opposite pole to the closest pole of the known magnet - induced magnetism)

Very few elements on the periodic table are magnetic

Question 10

What is the difference between a permanent and an induced magnet?

Answer 10

• Permanent magnets are made out of hard magnetic materials and will produce their own magnetic field
• Induced magnets are made when magnetically soft materials are placed into magnetic fields and temporarily become magnets, with one end become a south pole and one end becoming a north pole
• The end of the magnetic material closest to the magnet used to induced magnetism in the material will be the opposite pole to the closest pole in this magnet which is why magnetic materials are always attracted to permanent magnets

Question 11

How would you investigate the magnetic field pattern for one permanent bar magnet and between two permanent bar magnets?

Answer 11

• Place the bar magnet on a piece of paper, and draw dots at the poles of the magnets
• By placing a compass next to the dots so that the compass points away from the dots, draw another dot at the end of the compass at the tip of the needle
• Repeat this process on all parts of the poles of the compass and join up the dots
• Repeat the experiment but with two bar magnets, once with the same poles next to eachother and again with opposite poles next to eachother