Simple Magnetism and Magnetic Fields

State a substance from which the bar magnet could be made.

The thin rod is perpendicular to the top and bottom surfaces of the bar magnet.

Fig. 6.1 shows a view from above of the bar magnet with the N pole, the S pole and the thin rod labelled.

Draw on Fig. 6.1 to show the pattern and the direction of the magnetic field around the bar magnet.

Draw arrows on Fig. 6.2 to show the direction of the horizontal forces that act on the poles of the bar magnet.

Describe and explain what happens to the bar magnet when the electromagnet is switched on.

Describe how this is done.

You may draw a diagram if you wish.

Describe how you can check that the steel rod is magnetised.

State the material from which the compass needle is made.

Describe how the small compass is used to plot magnetic field lines in the region surrounding the magnet.

An unmagnetised iron bar PQ is placed near to the magnet on the laboratory bench.

Fig. 6.2 shows the two poles of the magnet and PQ.

The iron bar is initially at rest and the magnet is moved to the right very slowly.

When the magnet is a short distance from the iron bar, the iron bar moves very quickly to the left towards it.

Explain why the iron bar is attracted to the magnet.

On Fig. 4.1, mark an arrow on each of the magnetic field lines to show its direction.

Explain why placing the soft iron inside the box causes the paper clips to fall off.

Explain why it is sensible to have magnetic screening around the tube of a cathode-ray oscilloscope.

The magnet causes a force on the S-pole of the compass needle.

On Fig. 7.1, draw an arrow from the S-pole of the compass needle to show the direction of this force.

Explain why the compass needle turns when the finger is removed.

A small compass is used to plot the magnetic field lines of the magnet.

Describe how the compass is used to plot magnetic field lines on a piece of paper.

Suggest a material that is used to make a permanent magnet.

______

When there are no other magnetic fields present, the needle of a plotting compass points due north in the Earth's magnetic field. This is shown in Fig. 6.1.

The plotting compass is placed close to a permanent magnet, first at position A and then at position B, as shown in Fig. 6.2.

The magnetic field close to the permanent magnet is very much larger than the magnetic field of the Earth.

On Fig. 6.2, draw needles in the two circles to show the direction in which the compass needle points when the compass is at A and at B.

Describe an electrical method that is used to demagnetise a permanent magnet. You may include a diagram in your answer.

On Fig. 5.1, mark with an N the position of the north pole produced in the iron bar and mark with an S the position of the south pole produced in the iron bar.

State and explain what happens to the iron bar once it is magnetised.

The switch is opened and there is no current in the wire. State what happens to the magnetic poles in the iron bar.

aluminium,

______

iron,

______

steel.

______

The top magnet floats in the air above the bottom magnet.

On Fig. 6.1, mark the poles on the top magnet and explain why it floats in the air above the bottom magnet.

The top magnet is replaced with a ring made of iron.

Explain why the iron ring sticks to the bottom magnet.

Describe how a magnet is used to find out if a sample of material is magnetic or non-magnetic.

Region 2 causes a magnetic force on region 1.

State the direction of the magnetic force on region 1 and explain why it acts.

On Fig. 7.1, draw arrows on the field lines to show the direction of the magnetic field near the boundary between region 1 and region 2.