Starter quiz
- A material that allows an electric current to flow is called an electrical conductor. A material that does not allow an electric current to flow is called an electrical ______.
- 'insulator' ✓
The diagram shows a magnetic field between two magnets. The north–seeking and south–seeking poles are shown but the arrows are missing from the field lines. Which way should the arrows point?- from left to right ✓
- from right to left
- towards both magnets
- towards the middle
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- A magnetic field with equally spaced field lines is described as ______.
- even
- constant
- steady
- uniform ✓
- linear
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- Which of the following statements describes the motor effect?
- A current appears in a wire that is moving in an electric field.
- A current appears in a wire that is moving in a magnetic field.
- A magnetic field appears around a current–carrying wire.
- A current–carrying wire in an electric field experiences a force.
- A current–carrying wire in a magnetic field experiences a force. ✓
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- When using Fleming’s rule to predict the direction of the force, current or magnetic field in the motor effect, which of the following are correct?
- Only the left hand gives the correct result. ✓
- The first finger points in the direction of the force.
- The second finger points in the direction of the current. ✓
- The thumb, first finger and second fingers are at right angles to each other. ✓
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The diagram shows a current–carrying wire in a uniform magnetic field. Black arrows show magnetic field direction and a grey arrow shows current direction. In which direction is the force on the wire?- upwards
- downwards ✓
- to the right
- to the left
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Exit quiz
- Match each part of a motor with its description.
- axle⇔a rod about which the coil turns ✓
- coil⇔insulated wire wound into many turns; rotates when the motor runs ✓
- yoke⇔a U–shaped piece of iron that holds two magnets in place ✓
The diagram shows a simple electric motor from one end, with some of its parts labelled with the letters A to D. Match each letter with the name of the part.- A⇔yoke ✓
- B⇔coil ✓
- C⇔wire contact ✓
- D⇔axle ✓
- Which of the following explains why the coil of a motor turns when it is connected to a suitable power supply?
- The coil is made of a magnetic material which is repelled by the magnets.
- The coil is made of a magnetic material which is attracted by the magnets.
- The magnetic field exerts a force on the axle which makes it spin.
- The magnetic field exerts a force on the coil because it carries a current. ✓
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- A pupil tries to make an electric motor. They join the wire contacts onto the ends of the coil. Why does the motor not work correctly when a battery is connected to the other ends of the contacts?
- No current flows in the coil.
- Wires tangle when the coil spins. ✓
- No magnetic forces act on the coil.
- There is no electrical contact between the coil and the battery.
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The diagram shows a motor that is powered by a battery. When the coil is in the vertical position shown, there is no electrical contact between the coil and the battery. What happens next, and why?- The coil stops turning because no force is acting on it.
- The coil falls back to horizontal because gravity acts on it.
- The coil keeps turning because hardly any force is acting on it. ✓
- The coil keeps turning because the magnetic field still exerts a force on it.
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- A pupil makes a simple electric motor. When they connect it to a suitable power supply, the coil does not spin. Which of the following are possible reasons why?
- The coil is made from insulated wire.
- The ends of the wire contacts are not insulated.
- The magnets have their north poles facing each other. ✓
- The rod through the centre of the core is not insulated. ✓
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Worksheet
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Presentation
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Video
Lesson Details
Key learning points
- Wire in a motor is insulated so that the current flows around the coil
- Connections in a motor slide over each other to prevent tangled wires
- When the coil in a motor kit is horizontal it is connected and a force acts on the sides 90 deg. to the magnetic field
- Every half–turn, the coil connections in a motor kit swap over and change the direction of current through the coil
- Each side of a coil in a motor kit at 90º to the magnetic field is pushed alternatively up then down every half turn
Common misconception
Pupils find it challenging to think about how current flows through the connections and around the coil in the motor.
Take pupils step–by–step through the building of a motor from a motor kit and provide an opportunity for pupils to build their own working motor to help them to consolidate their understanding.
Keywords
Electrical insulator - is a material that does not conduct electric current
Motor coil - a coil of insulated wire that spins inside an electric motor when a current flows through it
Axle - a rod at the centre of wheels and gears around which they turn
Yoke - in a motor kit, a U–shaped piece of iron that holds two magnets in place to create a uniform magnetic field
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