Science 9 · Unit 9: Electricity · Cambridge Lower Secondary Science Stage 9

Questions

1. 1. Which everyday device uses a variable resistor?

   • a fuse
   • a battery
   • a light bulb
   • a dimmer switch for lights
   Check

2. 2. The resistance of a variable resistor in series with a lamp is decreased. What happens to the lamp?

   • The lamp stays the same brightness.
   • The current increases, so the lamp gets brighter.
   • The current decreases, so the lamp gets dimmer.
   • The lamp goes out.
   Check

3. 3. When a fridge door is opened, a light comes on inside. What does opening the door do to the switch?

   • It opens the switch, so current flows through the lamp.
   • It changes the voltage of the mains supply.
   • It closes the switch, so current flows through the lamp.
   • It closes the switch, so current stops.
   Check

4. 4. Two equal resistors are in series with a 12 V battery. What is the voltage across each resistor?

   • 12 V
   • 3 V
   • 24 V
   • 6 V
   Check

5. 5. Which could describe the resistance of a variable resistor?

   • 1–50 Ω
   • 1–50 V
   • 50 V only
   • 50 W only
   Check

6. 6. A variable resistor is in series with a lamp. Its resistance is increased. What happens to the current through the lamp?

   • It decreases.
   • It increases.
   • It stays the same.
   Check

7. 7. What happens to the brightness of the lamp when the variable resistor's resistance is increased?

   • It gets dimmer.
   • It gets brighter.
   • It stays the same.
   Check

8. 8. What is the difference between a variable resistor and a fixed resistor?

   • A fixed resistor has no resistance.
   • A variable resistor only works with lamps.
   • A variable resistor's resistance can be changed. A fixed one's can't.
   • A variable resistor measures current.
   Check

9. 9. How can one variable resistor change the brightness of two lamps in series?

   • Put it in series with both lamps, in the same loop.
   • Leave it out of the circuit.
   • Connect it to a separate battery.
   • Put it across one lamp only.
   Check

10. 10. How can one variable resistor control the brightness of two lamps in parallel?

    • Leave it out of the circuit.
    • Put it in parallel with both lamps.
    • Put it in series with the cell, before the branches split.
    • Put it in one branch only.
    Check

11. 11. All the lamps in circuits A–D are identical. Which circuit will show the voltage across one component?

    • B
    • A
    • D
    • C
    Check

12. 12. Which circuit will show the current through the cell?

    • B
    • C
    • D
    • A
    Check

13. 13. Which circuit contains lamps of different brightness?

    • D
    • C
    • B
    • A
    Check

14. 14. Which circuit will show the total current that flows through two components?

    • D
    • C
    • B
    • A
    Check

15. 15. Which circuits contain two lamps that have the same current?

    • A only
    • B and D
    • A, C and D
    • C and D only
    Check

16. 16. Which circuit contains a lamp with the same voltage across it as the cell?

    • B
    • D
    • C
    • A
    Check