MagnetsLesson 2

TargetTo know about magnetic

fields

Magnetic Fields - Experiment

Put a magnet under a piece of paper.

Carefully scatter iron filings on the paper.

Draw what you see.

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

What does the magnetic field around a bar magnet look like ? [shape and direction].

N S

Strongest at poles

Weaker further away

Drawing a magnetic field

Magnetic field lines

From N to S

N S

Notes

Magnetic Fields - Experiment

Put the north and south poles of two bar magnets together. What happens?

Now put the two magnets under a piece of paper with N and S 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 a single magnet’s field?

ATTRACTINGNotes

Magnetic field pattern with N poles together

NNS S

Notice the pattern of lines offorce in this region.

REPELLINGNotes

Magnetic Fields - Summary

1. When two like poles (two North poles or two South poles) are put together, they repel each other.

2. When two unlike poles (a North and a South pole) are put together, they attract each other.

3. Scattering iron filings around the bar magnets allows us to see the lines of force of the magnetic field. A plotting compass allows us to draw the field.

Notes

Paul drops a bar magnet into a box of nails. When he picks the magnet up, some nails are sticking to the ends.

(a) What material are the nails made from? (b) The nails stick to the ends of the bar magnet

but not to the middle.Why do the nails stick to the ends of the magnet?

Paul drops a bar magnet into a box of nails. When he picks the magnet up, some nails are sticking to the ends.

(a) What material are the nails made from? (b) The nails stick to the ends of the bar magnet

but not to the middle.Why do the nails stick to the ends of the magnet?

Iron

The magnetic field is strongest at the ends of the magnet.

Paul puts a magnet on a piece of cork. He floats the cork on water in a plastic bowl, and spins it round slowly.

When the cork stops spinning, in which direction will the magnet point?

Paul puts a magnet on a piece of cork. He floats the cork on water in a plastic bowl, and spins it round slowly.

When the cork stops spinning, in which direction will the magnet point?

N pole points to the Earth’s North pole.

Paul takes a second, identical bar magnet. The two magnets stick together as shown. One of the poles has been labeled on the drawing.

N

Label the other three poles.

Paul takes a second, identical bar magnet. The two magnets stick together as shown. One of the poles has been labeled on the drawing.

N

Label the other three poles.

S

S N

Paul puts the two magnets on the piece of cork. He floats the cork on the water in the plastic bowl, and again spins it round slowly.

In which direction will the magnets point at the end of the experiment?

Paul puts the two magnets on the piece of cork. He floats the cork on the water in the plastic bowl, and again spins it round slowly.

In which direction will the magnets point at the end of the experiment?

Magnets point in any direction.

Homework task

Go to website – physicslab.co.uk

Download magnets simulation on magnetic fields.

Find out the magnetic field diagrams for two magnets placed side by side as shown below. Then either sketch

the diagrams in your book OR print the diagrams.

1. N

S

N

S

N

S

S

N

2.