P11.0 – Magnetism

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1. Describe the properties of magnets.

You know magnets as objects that attract other magnetic objects towards it when they’re close.

Magnets can attract or repel other objects and this happens because of it’s two poles- north pole and south pole. When two magnets are bought together and if they have opposite poles facing each other, then they will attract each other. If they’re the same poles, they will repel each other. Thus, unlike poles attract and like poles repel.

 

2. Give an account of induced magnetism.

Magnetism can be induced (produced) in an metals which have magnetic properties (example: iron) by simply placing the iron close to a strong magnet without touching. The iron will also have a south and north pole and will attract the opposite pole of the magenet.

3. Identify the pattern of field lines round a bar magnet.

 

Magnets have magnetic field lines around them and when two magnet’s field lines intersect each other, they attract each other. Magnetic field lines always run from the  north pole to the south pole.

 

 

4. Distinguish between the magnetic properties of iron and steel

Steel (which is made from iron) is also a magnetic material due to its iron content but is harder to magnetise and demagnetise, thus is called a hard iron. In contrast, iron is known as soft iron, since its easy to magnetise and demagnetise.

Soft iron (iron):
Easy to magnetise
Cannot retain magnetism in the absence of magnets, i.e. its magnetism can be turned on and off by moving the magnet closer and farther from it. This property makes soft iron of more use in electromagnets (explained below).

Hard iron (steel):
Hard to magnetise
Retains magnetism even in the absence of magnets, which is why steel is used to make permanent magnets whose magnetism will last a long time.

 

5. Distinguish between the design and use of permanent magnets and electromagnets.

Electromagnets are objects that become magnetic when electricity is flown through it. They are temporary, as their magnetism can be turned on and off by switching an electrical circuit on and off.
Permanent magnets’ magnetism cannot be turned on and off, they are permanently magnetised.

 

 

Notes sumbitted by Lintha

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