Electromagnetism

This question is about magnets and magnetism.

Figure 3 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 3.

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 3 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 4 shows the magnetic field around a wire carrying a current.

State how you can tell from Figure 4 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 5.

Describe the relationship between magnetic field strength and current.

A teacher prepares some equipment to demonstrate electromagnetism. Figure 2 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 3 shows the display on the screen of the phone.

(Source: adapted from MGS Lite app for iPhone)

Figure 3

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 4 shows the magnet and the new display on the screen.

(Source: adapted from MGS Lite app for iPhone)

Figure 4

State two changes in the magnetic field measured by the phone from Figure 3 to Figure 4.

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

Figure 3 shows some objects and words describing these objects.

Draw one line from each object to its description.

object description

Figure 4 shows a wire passing through a piece of card. The wire carries an electric current.

Figure 4

Draw one magnetic field line on Figure 4, to show the shape of the magnetic field produced by the current.

Draw one arrow on the field line you have drawn to show the direction of the magnetic field.

A student measures the strength of the magnetic field at several distances from the wire in Figure 4. Figure 5 shows most of the student’s results.

Figure 6 shows two extra sets of results. mT is a unit of strength of a magnetic field.

Plot the two extra points on Figure 5.

Draw a best fit curve on the graph in Figure 5.

Use the graph in Figure 5 to calculate the change in strength of magnetic field when the distance from the wire changes from 4 cm to 8 cm.

change in strength of magnetic field =_........ mT

The distance from the wire affects the strength of the magnetic field.

State one other factor that affects the strength of the magnetic field.

Figure 6 shows the magnetic field of a magnet.

At which point is the magnetic field strongest?

Figure 7 shows a wire carrying a current.

Draw, on the card in Figure 7, the magnetic field that is produced by the current.

Figure 8 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

force on the roller =_........ N

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 8 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 3 shows two magnetic poles facing each other.

The magnetic field between the poles is uniform.

On Figure 3, draw the magnetic field lines between the two poles and show the direction of this magnetic field.

Figure 3

A student uses a plotting compass to investigate the magnetic field around a wire.

Figure 3 shows the wire going straight through a card.

Figure 3 shows the compass needle when there is no current in the wire.

Which of these shows a possible direction of the compass needle when there is a current in the wire going from P to Q?

Describe how the student could develop the investigation to find the shape of the magnetic field produced by the current.

Figure 4 shows a copper wire between two magnetic poles.

The current in the wire is in the direction shown by the arrow.

The wire experiences a force due to the magnetic field.

The direction of the force due to the magnetic field is

The interaction between the magnetic fields produced by the magnet and the current in the wire produces forces on the magnet and the wire.

Compare these two forces.

Figure 5 shows a different wire inside a uniform magnetic field.

The magnetic flux density of the magnetic field is 0.72 N/A m. The length of the wire inside the field is 30 mm. The size of the force due to the magnetic field on the wire is 0.045 N.

Calculate the size of the current in the wire.

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

current in the wire =_........ A

Figure 1 shows the magnetic field produced by a current in a long, straight wire.

Which row of the table is correct when the strength of the magnetic field is greatest?

Which of these materials would be the most suitable for making a temporary magnet?

Figure 2 shows a magnet holding some paper clips.

Describe how a student could show that the paper clips are induced magnets.

Describe how you could show that the Earth has a magnetic field.

A student uses a compass to investigate the magnetic field near a bar magnet.

The student places the compass near the bar magnet as shown in Figure 3.

Figure 3

Mark the north pole of the bar magnet with an ‘N’ in Figure 3.

State two ways in which the investigation could be developed to show the shape of the magnetic field around the bar magnet.

You may add to Figure 3 to help with your answer.