Magnetism

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Magnets

N S

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Mmagnetism : Magnetic?

Which of the metals below are magnetic metals?

Silver (Ag)





What is a magnetic Field ?

NS

The iron filings locate the magnetic field and show the

direction of the forces in this region.

The region around a

magnet where it has

a magnetic effect is

called its magnetic

field.

If you put a

magnetic material in

that field it will

experience a force.





Magnetic Fields - Experiments

Put the north poles of two bar magnets together.

What happens?

Now put the two magnets under a piece of paper

with the N poles together.

Carefully scatter iron filings on the paper.

Draw what you see.





Magnetic field pattern with N and S poles

together

NNS S

Notice the pattern of lines of force in this region.

How are they different from before?





SN

Stroke a steel knitting needle with a magnet as indicated in the sketch. Do this at least 20 times – using the same motion. The needle will become magnetic and will keep its magnetism.





Electromagnetism : Magnetic Fields

What does the magnetic field around a current

carrying coil [solenoid] look like?

Using an iron nail as a solenoid investigate the properties of the

magnetic field.

Keeping the current the same, investigate how many paper clips the

solenoid will support as the number of coils is varied.

Then, keeping the number of coils of wire the same, investigate how

many paper clips the solenoid will support as the current is varied.

Record your results in the tables following:





Electromagnetism : Electromagnets

Current [A]Number of paper

clips attracted

0

Remember - keep the number of coils the same!






How the current affects the strength

of an electromagnet

-10

0

10

20

30

40

50

60

70

0 1 2 3 4 5

Current [A]

Nu

mber

of

clip

s attra

cted






We use large electromagnets in scrap yards to

pick up scrap metal:

What metals would the

electromagnet attract?

What advantages does

an electromagnet have

over a permanent

magnet?






Lifts, cars and other large electrical machines use

high currents.

A relay can be used to allow a low current circuit to

turn a large current circuit on.



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Magnetism