Permanent and induced magnetism, magnetic fields

Which of these is a magnetic material?

Figure 10 shows two magnetic poles facing each other.

There is a uniform magnetic field between the poles.

Draw field lines, on Figure 10, to show the uniform part of the magnetic field. At least one line must have an arrow on it to indicate the direction of the magnetic field.

Figure 10

Figure 11 shows the magnetic field around a bar magnet.

Iron filings are sprinkled onto the magnet.

On Figure 11, draw an X where most of the iron filings will stick.

Explain why most of the iron filings will stick to the point you have labelled with an X.

One use of a magnet is in a plotting compass.

Explain how a plotting compass can be used to show that the Earth has a magnetic field.

State the name of a device that uses a permanent magnet.

Figure 11 shows two nails, X and Y, hanging from a magnet.

Complete the labels in Figure 11 to show the N and S poles of nail Y.

Nail X is removed from the magnet and nail Y falls off nail X.

This shows that the magnet caused both nails to be

A teacher has a pile of steel nails, a magnet and some plastic strips that are all the same size.

The teacher places a plastic strip under the magnet and picks up some nails from the pile, as shown in Figure 12.

Some nails are not picked up and are left behind on the bench.

The teacher investigates how the number of nails that can be picked up changes when the number of plastic strips under the magnet is increased.

The results are shown in Figure 13.

Complete Figure 13 to show the missing value.

Use the data in Figure 13 to complete the bar chart in Figure 14.

Use Figure 14 to describe the relationship between the number of plastic strips and the mean number of nails picked up.

A student thinks that none of the nails used in the investigation become permanently magnetised.

Suggest how the student could test this hypothesis.

The magnetic flux density, B, is a measure of the strength of the magnetic field of a magnet.

B varies with the distance, d, from a magnetic pole of a magnet as given by the equation

where K is a constant for the magnet.

At a distance of 3 mm from the pole of a magnet, B = 650 μ T.

Calculate the value of B at a distance of 6 mm from the pole of the magnet.

B at 6 mm =_........

Figure 8 shows the shape of the magnetic field lines around a bar magnet.

Draw one arrow on a magnetic field line in Figure 8 to show the direction of that magnetic field line.

Draw an X on Figure 8 to show where the magnetic field is strongest.

Give a reason why Figure 8 shows the magnetic field is strongest at point X.

A student places two magnets on a smooth bench.

The student holds the magnets close to each other, as shown in Figure 9.

Figure 9

Draw some magnetic field lines on Figure 9 to show the shape of the magnetic field between the two magnets.

The student is holding the two magnets on the smooth bench.

State what would happen if the student let go of one of the magnets.

A student is given two permanent magnets and some paper clips, as shown in Figure 10.

The paper clips are not magnets, but they are made from a magnetic material.

Which of these is a magnetic material?

Describe how the student could use the paper clips to find out which of the two permanent magnets is the stronger magnet.

Figure 13 represents the Earth.

Figure 13 shows two magnetic compass needles placed near to the Earth’s surface, at points Q and T.

Each magnetic compass needle can rotate about its central dot.

A compass needle is placed at point P and another at point R, near to the Earth’s surface.

On Figure 13, draw an arrow at point P and an arrow at point R to show the direction of the compass needle at each point.

Explain why the arrows point in the directions you have drawn in part (i).

You may draw on Figure 13 to help your answer.

Figure 14 shows a wire placed between the poles of a U-shaped magnet.

The wire is connected to a resistor and a battery.

The wire carries a current in the direction shown.

The wire is perpendicular to the magnetic field of the magnet.

Draw an arrow on Figure 14 to show the direction of the force, F, acting on the wire.

Label this arrow ‘F’.

State one practical way of reversing the direction of force F.

In Figure 14

• current in the wire = 3.2 A

• length of wire in the magnetic field = 0.042 m

• magnitude of the force on the wire = 0.078 N

Calculate the magnitude of the magnetic flux density between the two poles of the magnet.

magnetic flux density =_........

This question is about magnets and magnetism.

Figure 8 shows a magnet that has picked up three paper clips.

The poles of the lowest paper clip are labelled.

Label the poles of the other two paper clips in Figure 8.

Complete the sentence, by choosing a word from the box, to describe the type of magnetism that these paper clips have.

These paper clips have_........ magnetism.

Suggest a material that these paper clips in Figure 8 could be made from.

When the paper clips were pulled off the magnet they fell separately to the table.

Describe how you could test whether any of the paper clips had kept any magnetism.

Figure 9 shows the magnetic field around a wire carrying a current.

State how you can tell from Figure 9 that the strength of the field is greater at P than at Q.

The magnetic field strength is measured at P for different values of current in the wire.

The results of this investigation are shown in Figure 10.

Describe the relationship between magnetic field strength and current.

Figure 8 shows two magnets with their N poles facing each other.

Figure 8

On Figure 8, draw the shape and direction of the magnetic field between the two magnets.

Figure 9 shows a toy that has a plastic cylinder, a plastic base and two similar magnets. Each of the two magnets is in the shape of a ring.

The upper magnet seems to float in the air above the lower magnet.

Describe the forces acting on the upper magnet.

Use the idea of magnetic fields in your answer.

Figure 10 shows a current‑carrying wire between the poles of a magnet.

The magnet and the wire each experience a force when there is a current in the wire.

1 State the direction of the force on the wire.

2 State the direction of the force on the magnet.

The force on the wire is 0.15 N.

The current in the wire is 2.7 A.

The magnet produces a field with a magnetic flux density of 0.50 T.

Calculate the length of the wire in the magnetic field.

Use an equation selected from the list of equations given at the end of the question paper.

length of the wire in the magnetic field =_........

A teacher prepares some equipment to demonstrate electromagnetism. Figure 9 shows the equipment.

The teacher wants to show that iron filings

• are picked up by the metal rod when the switch is closed

• fall off the metal rod when the switch is opened again.

Suggest a suitable metal for the rod.

Give two reasons for your choice.

A student’s mobile phone has an app to measure a magnetic field.

The student places the phone on a table and rotates the phone until it is pointing north.

There are no magnets near to the phone.

Figure 10 shows the display on the screen of the phone.

(Source: adapted from MGS Lite app for iPhone)

Figure 10

State why the strength of the magnetic field shown is not zero.

The student places a magnet near to the phone on the table.

Figure 11 shows the magnet and the new display on the screen.

(Source: adapted from MGS Lite app for iPhone)

Figure 11

State two changes in the magnetic field measured by the phone from Figure 10 to Figure 11.

Describe how the student could use the mobile phone to investigate the strength of the magnetic field at different distances from the magnet.

Figure 11 shows the shape of the magnetic field near a bar magnet.

Figure 11

Draw arrows on the field lines in Figure 11 to show the direction of the magnetic field.

Place a letter X on Figure 11 at a place where the magnetic field is strongest.

Describe two differences between the magnetic field shown in Figure 11 and a uniform magnetic field.

State how a uniform magnetic field may be obtained in a school laboratory.

Figure 12 shows the directions of some plotting compass needles placed at different points near the Earth’s surface.

Figure 12

Sketch, on Figure 12, the Earth’s magnetic field outside and inside the Earth.

State which part of the Earth generates its magnetic field.

A wire is placed at right angles to the Earth’s magnetic field.

The wire is 0.600 m long and carries a current of 93.1 mA.

The force on the wire is 1.11 × 10⁻⁵N.

Calculate the magnetic flux density of the Earth’s magnetic field.

Use the equation

F = B × I × l

magnetic flux density =_........

A student uses plotting compasses to investigate the magnetic field between the poles of two bar magnets.

Figure 12 shows one of the plotting compasses and one of the bar magnets.

The student places the two magnets on a piece of paper with a pole of one magnet a few centimetres away from a pole of the other magnet.

The student places 20 plotting compasses on the paper near the magnets.

Figure 13 shows the direction in which each of the plotting compasses points.

Figure 13

Draw two rectangles on Figure 13 to show the positions of the two bar magnets.

Label the N-pole and the S-pole of each magnet.

The student wants to determine the shape of the magnetic field for a larger area around the magnets.

Describe how the student should continue the investigation using just one plotting compass.

Two long, thin magnets are held with their N-poles facing each other. The force, F, between the magnets can be calculated using the equation

where K is a constant value d is the distance between the magnets.

The magnets are 4.0 cm apart.

The force between the magnets is 1.2 N.

Calculate the value of K.

State the unit.

The magnets are held the same distance apart but with the N-pole of one magnet now facing the S-pole of the other magnet.

The value of K does not change.

State how the force would compare with the force in part (i).

F igure 13 shows a part of a machine used to separate steel cans from aluminium cans.

The cans are carried along a moving belt.

The belt goes around a roller.

The roller is a magnet.

Each can falls into one of the containers.

Explain how this machine separates the steel cans from the aluminium cans.

A student investigates magnetism using two toys as shown in Figure 14.

There is a magnet attached to the top of each toy.

The student moves the toy brick towards the toy car.

The magnet on the toy brick repels the magnet on the toy car.

On Figure 14, label the north pole and the south pole on the magnet attached to the toy brick.

Explain why the toy car starts to move only when the toy brick gets near to the toy car.

The student thinks that two magnets on top of each other will produce a magnetic field that is stronger than the magnetic field from a single magnet.

The student has a metre rule and more magnets available.

Describe how the student could develop this investigation to test this theory.

Figure 11 shows the magnetic field of a magnet.

At which point is the magnetic field strongest?

Figure 12 shows a wire carrying a current.

Draw, on the card in Figure 12, the magnetic field that is produced by the current.

Figure 13 shows two metal rods carrying a current.

A metal roller touches both rods and completes the circuit. The roller is in the magnetic field produced by a magnet.

The magnetic flux density of the magnetic field at the roller is 1.2 T.

The current in the roller is 2.5 A.

The length of the roller carrying the current is 0.060 m.

Calculate the force on the roller.

Use the equation

Describe how Fleming’s left‑hand rule can be used to determine the direction of the force acting on the roller.

You may draw a diagram to help your answer.

Draw an arrow on Figure 13 to show the direction of the force acting on the roller.

Which of these is a magnetic material?

A student has

− a power pack

− a long piece of wire

− a stiff card

− iron filings

Describe how the student could use this equipment to show the shape of the magnetic field produced by a current in the wire.

You may draw a diagram to help with your answer.

Figure 5 shows two magnetic poles facing each other.

The magnetic field between the poles is uniform.

On Figure 5, draw the magnetic field lines between the two poles and show the direction of this magnetic field.

Figure 5

A student has a bar magnet, a piece of iron the same size as the magnet, and some paper clips.

Describe how the student could use these items to demonstrate temporary induced magnetism.

A student sets up the apparatus shown in Figure 9.

When the current in the solenoid is switched on, the solenoid attracts the iron nail.

Describe how the student could use this apparatus to investigate how the size of the current in the solenoid affects the force of attraction between the solenoid and the iron nail.

The spring constant of a different spring is 24 N/m.

The spring is extended from its unstretched length by 12 cm.

Calculate the energy transferred in extending the spring by 12 cm.

Use an equation selected from the list of equations at the end of this paper.