Electromagnetism

When there is a current in a wire, there is a magnetic field around the wire.

Figure 5 shows a wire passing through a piece of card.

There is a current in the wire.

Draw two magnetic field lines on the card in Figure 5 to show the magnetic field pattern around the wire.

A student positioned a straight wire in the magnetic field between two magnets.

The wire was perpendicular to the magnetic field.

There was a current of 0.56 A in the wire.

The magnetic force on the wire was 2.1 mN.

The length of wire in the magnetic field was 0.050 m.

Calculate the magnetic flux density of the magnetic field between the magnets.

Use the Physics Equations Sheet.

Give the unit.

The student replaced the straight wire with a loop of wire.

The loop of wire was on an axle so that the loop could rotate.

The student connected the loop of wire to a battery and a switch.

Figure 6 shows the apparatus.

When the switch is closed, magnetic forces on the loop make the loop begin to rotate.

Explain how.

You should refer to side A and side B of the loop of wire in Figure 6.

Figure 6 shows two magnets and a wire.

There is a current in the wire.

A force acts on the wire in Figure 6.

What is the direction of the force on the wire?

Tick () one box.

The length of the wire in the magnetic field between the magnets is 80 mm.

The current in the wire is 4.6 A.

The force on the wire is 0.092 N.

Calculate the magnetic flux density between the magnets.

Use the Physics Equations Sheet.

Give the unit.

Figure 7 shows an electromagnet close to a permanent magnet.

The electromagnet exerts a force on the permanent magnet.

The permanent magnet exerts an equal and opposite force on the electromagnet.

Which law is this an example of?

Tick () one box.

Give two changes to the electromagnet that would increase the force exerted on the permanent magnet.

Give two changes to the electromagnet that would reverse the direction of the force exerted on the permanent magnet.

Figure 4 shows iron filings sprinkled around a bar magnet.

Why are the iron filings attracted to the bar magnet? Tick (✓) one box.

Figure 5 shows a bar magnet. Draw magnetic field lines to show the magnetic field pattern around the bar magnet. You should add arrows to the field lines to show the direction of the magnetic field.

Figure 5

Figure 6 shows two bar magnets.

Figure 6

The magnets attract each other. What conclusion can be made about the two poles marked X and Y ? Tick (✓) one box.

Figure 7 shows some plotting compasses around a wire. There is no current in

the wire.

Why do the plotting compasses all point in the same direction?

When the switch is closed there is a current in the wire. The current creates a magnetic field. What shape are the magnetic field lines around the wire? Tick (✓) one box.

A student investigated the force exerted by an electromagnet on a paper clip.

The student varied the distance between the paper clip and the electromagnet. Figure 8 shows the equipment used.

The student recorded the reading on the newtonmeter for several different distances.

The current in the electromagnet was the same for each distance. Complete the sentence. Choose the answer from the box.

In the investigation, the current was variable.

What is the size of the downward force on the paper clip in Figure 8 ?

The distance between the paper clip and the electromagnet is increased. What happens to the size of the downward force?

Figure 5 shows a compass.

Why does the compass always point in the same direction when it is not near a magnet? Tick (✓) one box.

What material could the needle of the compass be made from? Tick (✓) one box.

Figure 6 shows a coil of wire.

There is a current in the coil. The circles show the position of four compasses.

Which statement describes the magnetic field around the coil? Tick (✓) one box.

Draw one arrow in each circle on Figure 6 to show the direction of the magnetic field at that point.

Give two ways the magnetic field around the coil could be made stronger.

A teacher demonstrated the motor effect. Figure 5 shows the equipment used.

Explain why there is a force on the wire when there is a current in the wire.

Explain how the direction of the force on the wire can be predicted.

Figure 6 shows a simple electric motor.

Explain one way that the motor could be changed to increase the rate at which the coil rotates.

Magnets attract some metals.

Which diagram shows the correct magnetic field pattern for a bar magnet?

Tick (✓) one box.

Figure 3 shows an iron bar near a permanent magnet.

The iron bar becomes an induced magnet.

Label the poles on the iron bar.

The magnet is turned around so that the north pole is closest to the iron bar.

Which statement about the iron bar is true?

Tick (✓) one box.

Figure 4 shows an electromagnet being used to separate pieces of different types of

metal on a conveyor belt.

Which two of the following types of metal would be attracted to the electromagnet?

Tick (✓) two boxes.

What is an advantage of using an electromagnet instead of a permanent magnet to separate the types of metal?

Tick (✓) one box.

Figure 5 shows a simple electromagnet.

What is the purpose of the iron nail inside the coil of wire?

Tick (✓) one box.

Which of the following would increase the strength of the electromagnet?

Tick (✓) one box.

Figure 4 shows the magnetic field pattern around a permanent magnet.

Where is the magnetic field of the magnet the strongest?

How does Figure 4 show that the strength of the magnetic field is not the same at all places?

Figure 5 shows an electromagnet being used to separate iron and steel from

non-magnetic metals.

Explain one reason why an electromagnet is used instead of a permanent magnet.

Pieces of iron and steel are attracted to the electromagnet. Name two other metals that would be attracted to the electromagnet.

The design of the electromagnet cannot be changed. Give two ways the force exerted by the electromagnet on a piece of iron or steel could be increased.

The conveyor belt that moves the pieces of metal is driven by an electric motor.

Figure 6 shows a simple electric motor.

The length of the wire AB in the magnetic field is 120 mm. There is a current of 4.0 A in the wire. The length of wire AB experiences a force of 0.36 N. Calculate the magnetic flux density between the magnets. Give the unit.

Fleming’s left-hand rule can be used to determine the direction of the force on wire AB. Complete the labels on Figure 7 to show Fleming’s left-hand rule.

A magnet produces a magnetic field.

Which diagram shows the magnetic field pattern around a bar magnet?

Tick one box.

Figure 13 shows three metal blocks.

The blocks are not labelled.

One block is a permanent magnet, one is iron and one is aluminium.

Describe how another permanent magnet can be used to identify the blocks.

Figure 14 shows a toy crane.

The toy crane uses an electromagnet to pick up and move the blocks.

Explain how this electromagnet is able to pick up and move the blocks.

A magnet produces a magnetic field.

Which diagram shows the magnetic field pattern around a bar magnet? Tick one box.

Figure 3 shows three metal blocks. The blocks are not labelled. One block is a permanent magnet, one is iron and one is aluminium.

Describe how another permanent magnet can be used to identify the blocks.

Figure 4 shows a toy crane.

The toy crane uses an electromagnet to pick up and move the blocks. Explain how this electromagnet is able to pick up and move the blocks.