Electromagnetism & The Motor Effect (Edexcel GCSE Physics)

Higher Tier Only

Figure 11 shows the magnetic field of a magnet.

Figure 11

At which point is the magnetic field strongest?

Higher Tier Only

Figure 12 shows a wire carrying a current. 

Figure 12

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

Higher Tier Only

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.

Figure 13

i) 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

F = B × I × l

force on the roller = ................................... N[2]

ii) 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.

[3]

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

[1]

Figure 6 shows some objects and words describing these objects.

Draw one line from each object to its description.

Figure 6

Figure 7 shows a wire passing through a piece of card.

The wire carries an electric current.

Figure 7

i) Draw one magnetic field line on Figure 7, to show the shape of the magnetic field produced by the current.

[1]

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

[1]

A student measures the strength of the magnetic field at several distances from the wire in Figure 7.

Figure 8 shows most of the student’s results.

Figure 8

Figure 9 shows two extra sets of results. mT is a unit of strength of a magnetic field.

Figure 9

i) Plot the two extra points on Figure 8.

[2]

ii) Draw a best fit curve on the graph in Figure 8.

[1]

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

change in strength of magnetic field = ................ mT[2]

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

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

[1]

A teacher is demonstrating electromagnetic induction.

The teacher has a bar magnet, a coil of wire and a sensitive voltmeter.

i) Draw a diagram to show how the teacher should arrange the apparatus.

[1]

ii) Explain how the teacher could use this apparatus to demonstrate the factors affecting the size and direction of the induced potential difference.

[4]

Higher Tier Only

There is a changing magnetic field in the core of a transformer.

i) Describe the cause of the changing magnetic field in the core of the transformer.

[2]

ii) A potential difference of 230V is applied across the primary coil of a transformer.

There is a potential difference of 15V across the secondary coil.

The primary coil has 2000 turns.

Calculate the number of turns in the secondary coil.

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

............................................... turns[3]

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Figure 1 shows equipment which demonstrates the motor effect.

Figure 1

A piece of copper wire (Q) is placed on two bare wires connected to a cell and switch.

Describe what happens to wire Q when the switch is closed.

Higher Tier Only

Describe any differences in the motion of Q for the following changes:

(i) The direction of the magnetic field is reversed.

[1]

 (ii) The cell is replaced with a cell of higher voltage. 

[1]

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Figure 2 shows two identical metal bars freely suspended inside a coil of insulated wire.

Figure 2

A direct current passes through the coil, then the metal bars move apart.

Explain why the metal bars move apart.

Higher Tier Only

The d.c. supply is removed and the metal rods return to their starting places.

Suggest a material that the metal rods could be made from. Explain why you chose this.

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The coil in Figure 1 is rotating. 

Figure 1

State the name of the phenomenon causing this rotation.

Higher Tier Only

Using Fleming's left hand rule, state the direction that the left side of the coil moves in Figure 1.

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A current of 2.5 A flows in the coil, which is 0.10 m long and 0.10 m wide.

If the magnetic flux density is 0.10 T, calculate the force on the left side of the coil.  

   Force = .................................... N

Higher Tier Only

Explain why a force acts on the coil when a current passes through it.

Figure 1 shows a coil of wires called a solenoid.

Figure 1

Figure 2 contains descriptions of the magnetic field. Place a tick (✓) in the correct cells in Figure 2 to identify the properties inside and outside the coil.

Figure 2

Describe how the student can use plotting compasses to determine the shape of the magnetic field around the coil. 

Higher Tier Only

A current-carrying wire is placed between two magnetic poles as shown in the diagram below. It experiences an upwards force.

What is the orientation of the magnetic poles? 

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Figure 1 shows a wire connected to a circuit inside a uniform magnetic field.

Figure 1

The magnetic flux density of the field is 0.82 N/A m. 

The length of the wire is 40 mm with 30 mm inside the field. 

The size of the force due to the magnetic field on the wire is 0.073 N.

Calculate

(i) The size of the current in the wire.

[3]

(ii) The direction of the force.

[1]

Higher Tier Only

The circuit in Figure 1 is turned so the wire is now placed horizontally.

Explain the effect this has on the motion of the wire.

A current-carrying wire is placed into a magnetic field as shown in the diagram. The wire experiences a force.

In which direction is the force?

Two long, thin magnets are held with their S-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.

When the magnets are 3.0 cm apart, the force between the magnets is 1.5 N.

Calculate the separation of the magnets when the force between them is 2.6 N.

Explain what happens if the magnets are held the same initial distance apart but with the S-pole of one magnet now facing the N-pole of the other magnet.