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

Questions

1. 1. Look at Marcus's results. As the number of turns on the coil increases, what happens to the number of paperclips lifted?

   • It decreases.
   • It stays the same.
   • It drops to zero.
   • It increases.
   Check

2. 2. Look at Marcus's results. What do they tell you about the electromagnet?

   • It gets stronger with more turns.
   • It gets weaker.
   • It stops working.
   • Turns make no difference.
   Check

3. 3. Look at Marcus's results. Which result looks anomalous (doesn't fit the pattern)?

   • 25 turns lifting 13 clips
   • 30 turns lifting 12 clips
   • 20 turns lifting 5 clips
   • 15 turns lifting 4 clips
   Check

4. 4. Marcus finds an anomalous result in his table. What should he do about it?

   • include it without checking
   • repeat that measurement
   • ignore all results
   • change the variable
   Check

5. 5. When investigating the number of turns, what should Marcus keep constant?

   • the current, the core material and the size of paperclips
   • only the switch
   • nothing
   • the number of turns
   Check

6. 6. Name another factor that affects the strength of an electromagnet.

   • the current in the coil
   • the colour of the wire
   • the shape of the switch
   • the time of day
   Check

7. 7. What safety risk increases as the current gets larger?

   • The wire in the coil gets too hot.
   • The magnet stops working.
   • The magnet lifts too many pins.
   • The pins get too hot.
   Check

8. 8. The electromagnet lifts 25 pins at 1.0 A. About how many might it lift at 2.0 A?

   • about 100
   • about 50
   • about 25
   • about 12
   Check

9. 9. Why is an adjustable power supply better than changing the number of cells?

   • It is magnetic.
   • It makes no current.
   • It changes the current smoothly in small steps and keeps the circuit the same.
   • It is always cheaper.
   Check

10. 10. Should Arun use large or small paperclips to measure strength?

    • small paperclips, for more precise results
    • a mix of sizes
    • large ones, because fewer are needed
    • it doesn't matter
    Check

11. 11. An electromagnet is held above an iron block on a balance. What happens to the reading when it's switched on?

    • It stays the same.
    • It decreases, because the magnet pulls the block upwards.
    • It increases.
    • It becomes negative instantly.
    Check

12. 12. As the current increases, what happens to the balance reading?

    • It increases.
    • It doesn't change.
    • It goes up then down.
    • It decreases further.
    Check

13. 13. Marcus says reversing the connections will reverse the change on the balance. Is he right?

    • No, it will stop working.
    • No, iron is attracted to either pole, so the reading still decreases.
    • Yes, the block will be pushed down.
    • Yes, it will float.
    Check

14. 14. Which core makes the strongest electromagnet?

    • iron
    • wood
    • aluminium
    • copper
    Check

15. 15. What is soft iron?

    • iron that is easily magnetised and easily demagnetised
    • iron that can be squashed like clay
    • iron that is never magnetic
    • iron mixed with plastic
    Check

16. 16. Four electromagnets have the same current and turns, with cores of rubber, wood, nickel and aluminium. Which is strongest?

    • the wood core
    • the rubber core
    • the nickel core
    • the aluminium core
    Check

17. 17. Why must a scrapyard electromagnet be stronger than the one that holds a toaster's handle down?

    • It works at night.
    • It is made of plastic.
    • It has to lift very heavy objects like cars.
    • It is used outside.
    Check