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Magnetism: GCSE Combined Science Physics practice questions

Foundation and Higher · Grade 5

A second set of questions on magnetism. They are different from the ones on the topic page. Try each, then open the answer and compare your working.

More questions

Question 1 Hard

A transformer has 140 turns on the primary coil and 30 on the secondary. The input is 1260 V. Work out the output potential difference.

Show answer

Answer: 270 V

  1. Secondary potential difference = primary potential difference × secondary turns ÷ primary turns.
  2. 1260 × 30 ÷ 140 = 270 V.

Question 2 Hard

A transformer has 40 turns on the primary coil and 20 on the secondary. The input is 360 V. Work out the output potential difference.

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Answer: 180 V

  1. Secondary potential difference = primary potential difference × secondary turns ÷ primary turns.
  2. 360 × 20 ÷ 40 = 180 V.

Question 3 Hard

A transformer has 60 turns on the primary coil and 50 on the secondary. The input is 480 V. Work out the output potential difference.

Show answer

Answer: 400 V

  1. Secondary potential difference = primary potential difference × secondary turns ÷ primary turns.
  2. 480 × 50 ÷ 60 = 400 V.

Question 4 Hard

A transformer has 40 turns on the primary coil and 50 on the secondary. The input is 280 V. Work out the output potential difference.

Show answer

Answer: 350 V

  1. Secondary potential difference = primary potential difference × secondary turns ÷ primary turns.
  2. 280 × 50 ÷ 40 = 350 V.

Question 5 Hard

The motor effect happens because the magnetic field of the wire … with the field of the magnet.

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Answer: interacts

  1. Two magnetic fields in the same region affect each other.
  2. The fields interact.

Question 6 Hard

Name one way to make a bigger potential difference when a magnet moves in and out of a coil.

Show answer

Answer: move the magnet faster

  1. Induction is bigger when the field changes faster.
  2. Move the magnet faster, use a stronger magnet or more turns.

Quick checks

Short questions with options. Choose one before you open the answer.

Check 1

What do we call the two ends of a magnet?

  1. poles
  2. plates
  3. cores
Show answer

poles The ends of a magnet, where its pull and push is strongest, are its poles.

Check 2

Two south poles are held close together. What happens?

  1. They attract.
  2. They repel.
  3. Nothing happens.
Show answer

They repel. Two south poles are like poles, and like poles repel.

Check 3

Which of these metals is magnetic?

  1. copper
  2. aluminium
  3. nickel
Show answer

nickel Iron, steel, cobalt and nickel are the magnetic metals.

Check 4

What is the region around a magnet where it can push or pull?

  1. its magnetic field
  2. its pole
  3. its core
Show answer

its magnetic field The magnetic field is the region where a magnet or magnetic material feels a force.

Check 5

Which way do field lines run outside a bar magnet?

  1. from south to north
  2. from north to south
  3. from the middle of the magnet to the ends only
Show answer

from north to south Outside a magnet the field lines run from the north pole to the south pole.

Check 6

Where is the field of a bar magnet strongest?

  1. halfway along the side, where the lines spread out
  2. far away from the magnet
  3. at the poles, where the lines are closest
Show answer

at the poles, where the lines are closest Field lines are closest together at the poles, so the field is strongest there.

Check 7

What is an induced magnet?

  1. a magnetic material that acts as a magnet only while it is in another magnet's field
  2. a magnet that keeps its magnetism for ever
  3. a magnet made from copper wire
Show answer

a magnetic material that acts as a magnet only while it is in another magnet's field An induced magnet loses most of its magnetism when the other magnet is removed.

Check 8

What does a compass needle line up with?

  1. the nearest metal object
  2. the magnetic field it is in
  3. the direction the wind blows
Show answer

the magnetic field it is in A compass needle is a small magnet that lines up with the field, such as the Earth's.

Check 9

A student says: use a steel core so the electromagnet stays magnetic. What is wrong?

  1. Steel is not a magnetic material.
  2. Steel makes the field weaker than copper does.
  3. An electromagnet must switch off, so soft iron is used instead of steel.
Show answer

An electromagnet must switch off, so soft iron is used instead of steel. Steel stays magnetised after the current stops, so it would not switch off properly.

Check 10

How do you make an electromagnet stronger?

  1. Add more turns of wire or increase the current.
  2. Switch off the current and wait.
  3. Replace the iron core with a plastic rod.
Show answer

Add more turns of wire or increase the current. More turns and a bigger current both increase the strength of the field.

Check 11

What is the shape of the field around a long straight wire carrying a current?

  1. straight lines along the wire
  2. circles around the wire
  3. There is no field.
Show answer

circles around the wire The field of a straight wire is a set of circles around it.

Check 12

What is a solenoid?

  1. a long coil of wire
  2. a type of battery
  3. a rod of soft iron
Show answer

a long coil of wire A solenoid is a coil of wire. With a current it has a field like a bar magnet.

Check 13

The current in an electromagnet is reversed. What happens to its poles?

  1. They stay the same.
  2. The magnet is destroyed.
  3. The north and south poles swap.
Show answer

The north and south poles swap. Reversing the current reverses the direction of the field.

Check 14

What is the motor effect?

  1. A wire carrying a current in a magnetic field feels a force.
  2. A magnet makes a wire hot.
  3. A motor makes a magnetic field disappear.
Show answer

A wire carrying a current in a magnetic field feels a force. The field of the wire and the field of the magnet push on each other.

Check 15

When is there no force on a current-carrying wire in a magnetic field?

  1. when the wire is parallel to the field
  2. when the wire is at right angles to the field
  3. when the current is large
Show answer

when the wire is parallel to the field If the wire lies along the field lines, there is no force.

Check 16

How do you reverse the force on a wire in the motor effect?

  1. Reverse both the current and the field.
  2. Reverse the current or the field, but not both.
  3. Make the wire longer.
Show answer

Reverse the current or the field, but not both. Reversing just one of them reverses the force. Reversing both gives the same direction as before.

Check 17

What is the unit of magnetic flux density?

  1. newton, N
  2. ampere, A
  3. tesla, T
Show answer

tesla, T Magnetic flux density is measured in tesla.

Check 18

Write the equation for the force on a wire in a field (Higher tier).

  1. F = B × I × L
  2. F = B ÷ (I × L)
  3. F = B + I + L
Show answer

F = B × I × L Force = magnetic flux density × current × length.

Check 19

A 2 m wire carries 5 A at right angles to a 0.4 T field. What is the force? (Higher tier)

  1. 10 N
  2. 4 N
  3. 0.8 N
Show answer

4 N F = 0.4 × 5 × 2 = 4 N.

Check 20

Which coil of a transformer is the input?

  1. the primary coil
  2. the secondary coil
  3. the iron core
Show answer

the primary coil The primary coil takes the input and the secondary coil gives the output.

Check 21

What does a step-up transformer do? (Higher tier)

  1. It decreases the potential difference.
  2. It changes a.c. into d.c.
  3. It increases the potential difference and has more secondary turns.
Show answer

It increases the potential difference and has more secondary turns. More secondary turns than primary turns gives a bigger output potential difference.

Check 22

A transformer has 100 primary turns and 300 secondary turns. The input is 20 V. What is the output? (Higher tier)

  1. 60 V
  2. 6.7 V
  3. 6000 V
Show answer

60 V Vs = 20 × 300 ÷ 100 = 60 V.

Check 23

Why does the national grid use a very high potential difference? (Higher tier)

  1. It makes the cables colder than the air.
  2. The current is smaller, so less energy is wasted as heat in the cables.
  3. It makes the electricity travel faster.
Show answer

The current is smaller, so less energy is wasted as heat in the cables. For the same power, a higher potential difference means a smaller current.

Check 24

A scrapyard crane drops a car when the driver flips a switch. Explain why.

  1. The car becomes lighter when the switch moves.
  2. The wire gets longer so the magnet reaches further.
  3. The current stops, so the soft iron core loses its magnetism.
Show answer

The current stops, so the soft iron core loses its magnetism. An electromagnet only has a strong field while the current flows.

Check 25

What is a permanent magnet?

  1. A material that is magnetic only inside another magnet's field
  2. A magnet that has its own magnetic field
  3. Any piece of metal
Show answer

A magnet that has its own magnetic field A magnet that produces its own magnetic field.

Check 26

How is an induced magnet different from a permanent magnet?

  1. It repels both poles.
  2. It keeps its magnetism forever.
  3. It only acts as a magnet inside another magnet's field.
Show answer

It only acts as a magnet inside another magnet's field. An induced magnet is only a magnet while it is in another magnetic field, and it loses most of its magnetism when removed.

Check 27

What force acts between a magnet and a piece of iron?

  1. Attraction
  2. Repulsion
  3. No force
Show answer

Attraction A force of attraction, always.

Check 28

Where is the field of a bar magnet strongest?

  1. In the middle of the magnet
  2. At the poles
  3. Far from the magnet
Show answer

At the poles At the poles.

Check 29

How does a compass show that the Earth's core is magnetic?

  1. The needle is pulled by the Sun.
  2. The needle is pulled by the Moon.
  3. The needle lines up with a field made inside the Earth.
Show answer

The needle lines up with a field made inside the Earth. Far from magnets, the needle lines up and points north, so the Earth must make a magnetic field.

Check 30

What is the shape of the magnetic field around a straight wire carrying a current?

  1. Circles around the wire
  2. Straight lines along the wire
  3. Lines like a bar magnet
Show answer

Circles around the wire Circles around the wire.

Check 31

What is the field inside a solenoid like?

  1. Weak and uneven
  2. Strong and uniform
  3. Zero
Show answer

Strong and uniform Strong and uniform.

Check 32

How do you use the right-hand grip rule for a wire?

  1. Thumb along the field, fingers show the current.
  2. Use your left hand with the thumb along the force.
  3. Thumb along the current, fingers show the field.
Show answer

Thumb along the current, fingers show the field. Point your right thumb along the current. Your curled fingers show the direction of the field.

Check 33

What is an electromagnet?

  1. A coil of wire with an iron core
  2. A magnet that gets power from a battery without any wire
  3. A permanent magnet made from iron
Show answer

A coil of wire with an iron core A solenoid with an iron core.

Check 34

What are the factors that affect the size of the force on a wire in a magnetic field?

  1. Only the colour of the wire
  2. Flux density, current and length of wire in the field
  3. Only the current
Show answer

Flux density, current and length of wire in the field The magnetic flux density, the current, and the length of wire in the field.

Check 35

Higher tier. What do the First finger, seCond finger and thuMb show in Fleming's left-hand rule?

  1. Force, current and motion
  2. Current, field and force
  3. Field, Current and Motion
Show answer

Field, Current and Motion Field, Current and Motion (the force).

Check 36

Higher tier. Why does a coil in a motor start to turn?

  1. The forces on the two sides act in opposite directions.
  2. The forces on both sides push the same way.
  3. The magnets spin round.
Show answer

The forces on the two sides act in opposite directions. The forces on the two sides of the coil point in opposite directions.

Check 37

Higher tier. What does a split-ring commutator do?

  1. It reverses the magnets every half turn.
  2. It reverses the current every half turn.
  3. It makes the current bigger.
Show answer

It reverses the current every half turn. It reverses the current in the coil every half turn, so the coil keeps turning the same way.

Check 38

Where does the force on a current-carrying wire in a magnetic field come from? (Higher tier)

Show answer

The interaction of the wire's magnetic field with the field of the magnet.

Check 39

What affects the size of an induced potential difference? (Higher tier)

Show answer

The strength of the magnet, the number of turns of the coil and the speed of movement.

Check 40

How can the direction of an induced potential difference be reversed? (Higher tier)

Show answer

Reverse the direction of movement or turn the magnet the other way round.

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