The Motor Effect (AQA GCSE Physics): Exam Questions

Figure 1 below shows a straight current carrying wire. The current is coming out of the page.

Figure 1

Complete Figure 1 to show the pattern of magnetic field lines around the wire.

How would the pattern change if the direction of the current in Figure 1 was reversed?

The picture below shows a long coil of wire called a solenoid.

When a current passes through the solenoid it produces a magnetic field.

Suggest three changes that would increase the strength of the magnetic field.

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Figure 2 below shows a straight wire passing between the poles of two magnets.

Figure 2

When a current passes through the wire a force is exerted on the wire.

What is the name given to this effect?

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Describe how the direction of the magnetic force can be determined using Fleming’s left-hand rule.

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Draw an arrow to Figure 2, showing the direction of the force.

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Explain why the magnetic force drawn on part (c) acts on the wire.

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Suggest three changes that would increase this magnetic force acting on the wire.

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The apparatus shown in Figure 3 below can be used to measure the force acting on a current-carrying wire placed in a magnetic field.

Figure 3

The balance is initially zeroed so that when the power supply is off, it shows no reading.

When the power supply is turned on, the balance shows a reading.

As the current is increased, the reading increases.

Explain in terms of forces why the reading increases.

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For the above apparatus, when the current in the wire was 0.25 A, a force of 1.96 mN was exerted on the wire

The length of wire between the poles of the magnet was 0.042 m

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

Give your answer to 2 significant figures.

(You may need to look up the appropriate formula on the Physics Equations Sheet).

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Figure 4 below shows a simple d.c. motor.

Figure 4

When a direct current is supplied to the coil, the coil starts to spin.

Explain why.

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Describe three changes that would make the coil in Figure 4 spin faster.

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Describe two changes that could reverse the direction of the coil in Figure 4.

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Figure 5 below shows a loudspeaker.

Figure 5

The loudspeaker produces a sound when an alternating current is connected to the coil.

Explain why.

Figure 6 below shows an electric bell.

Figure 6

When the switch is closed, the bell rings continuously.

Explain why.

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Explain what would happen if the batteries were inserted the wrong way around in Figure 6 and the switch closed again.

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Figure 1 shows a device known as a current balance.

Figure 1

The switch is closed. Describe and explain the subsequent motion of the section of wire labelled A to B.

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A small mass of 0.080 kg is used and placed 3.0 cm from the metal support. 

The section of wire labelled A to B is 6.0 cm long and is placed 8.0 cm away from the metal support.

The system is in equilibrium after the switch has been closed. 

Assume the mass of the plastic and the mass of the wire are negligible.   

Calculate the magnetic flux density at the location of wire section AB when a current of 0.2 A passes through it. 

Give your answer to Y significant figures.

Take the value of acceleration due to gravity to be 10 m/s² for this question.

Use the Physics Equation Sheet. 

   Magnetic flux density = .................................... T

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Figure 1 shows a wire passing between a North and South pole, with a flux density of 0.10 T between the poles.

The magnets cover 30 cm of the wire's length.

The wire has a resistance of 0.2 Ω and dissipates 5 J of energy every second. 

The current travels out of the plane of the page.

Figure 1

Calculate the magnitude of the force on the wire and state its direction.

Give your answer to 2 significant figures.   

   Force (2 significant figures) = .................................... N

   Direction: ....................................

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Figure 2 shows a diagram of a loudspeaker in a live music venue.

Figure 2

Explain why an alternating current in the coil causes the speaker cone to oscillate.