Science 8 · Unit 9: Magnetism · Cambridge Lower Secondary Science Stage 8

Questions

1. 1. Apart from a cell, wires and a switch, what two things are needed to make an electromagnet?

   • a bulb and a buzzer
   • a coil of insulated wire and an iron core
   • a magnet and a compass
   • plastic and paper
   Check

2. 2. What could be used to test an electromagnet?

   • wooden matchsticks
   • pieces of paper
   • steel paperclips
   • grains of salt
   Check

3. 3. Which metals could be magnetised as a core?

   • gold and copper
   • iron and steel
   • copper and aluminium
   • aluminium and gold
   Check

4. 4. How is an electromagnet different from a permanent magnet?

   • It is always on.
   • It has no poles.
   • It is made of plastic.
   • It can be switched on and off.
   Check

5. 5. Why does the nail pick up pins when the switch is closed?

   • The cell attracts pins.
   • The pins become electric.
   • The nail gets hot.
   • Current flows in the coil and magnetises the iron nail.
   Check

6. 6. Why do the pins fall off when the switch is opened?

   • No current flows, so the magnetic field stops.
   • The pins get heavier.
   • The nail becomes plastic.
   • Gravity stops.
   Check

7. 7. How could Marcus test if the pointed end of the nail is a north pole?

   • bring the north pole of a bar magnet near it and see if it repels
   • measure its temperature
   • see if it picks up pins
   • look at its colour
   Check

8. 8. Zara says the end must be a north pole because it attracts paperclips. Why could she be wrong?

   • Only south poles attract.
   • Both north and south poles attract paperclips.
   • Paperclips are not magnetic.
   • Electromagnets have no poles.
   Check

9. 9. How could Zara make the pointed end a south pole?

   • use a bigger nail
   • add more paperclips
   • paint the nail
   • reverse the cell or wind the coil the other way
   Check

10. 10. Name an application of electromagnets.

    • wooden spoons
    • glass windows
    • plastic bottles
    • scrapyard cranes that lift cars
    Check

11. 11. Why must the wire in an electromagnet coil be insulated?

    • to make it magnetic
    • to keep it cold
    • so the current goes round the coil instead of short-circuiting
    • so it looks nice
    Check

12. 12. Why is an iron core used rather than steel for an electromagnet?

    • Iron conducts no electricity.
    • Iron is not magnetic.
    • Iron loses its magnetism easily when switched off.
    • Steel is plastic.
    Check

13. 13. Does an electromagnet have north and south poles?

    • Yes
    • No
    Check

14. 14. A fire door is held open by an electromagnet. What happens when the fire alarm switches the electromagnet off?

    • The door locks open.
    • The door gets hot.
    • Nothing happens.
    • The door closes.
    Check

15. 15. What is the difference between 'magnetic' and 'magnetised'?

    • Magnetised means attracted to a magnet.
    • Magnetic means made of copper.
    • Magnetic means attracted to a magnet; magnetised means made into a magnet.
    • They mean the same.
    Check

16. 16. Which of these uses an electromagnet?

    • a glass window
    • a wooden door
    • an electric bell
    • a plastic bottle
    Check