← Back to the activity

Year 11 Science — Electricity

Use Ohm's law and the series and parallel rules to find a resistance or a current, work out electric power and energy, and say why a heater's element is an alloy and a fuse is a weak link.

Name: ________________________

  1. 1.A 6 Ω resistor and a 3 Ω resistor are joined in parallel. What is the equivalent resistance, in ohms? Answer with a number.

  2. 2.Sort each statement by the kind of circuit it describes.

    Groups: Series · Parallel

    • The currents through the branches add up to the total current
    • The potential differences across the resistors add up to the supply voltage
    • The potential difference is the same across each resistor
    • The current is the same through each resistor
    • When one component fails, nothing in the circuit works
    • Each gadget can draw the current it needs

  3. 3.What does a fuse do, and where is it placed?

    • a) Its wire melts under an unduly high current, breaking a circuit it sits in parallel with
    • b) Its wire melts under an unduly high current, breaking a circuit it sits in series with
    • c) It stores charge until the current returns to normal
    • d) It lowers the resistance of the circuit so less current flows

  4. 4.Sort each material by what the chapter says it is used for.

    Groups: Filaments of electric bulbs · Electrical transmission lines · Heating devices such as an electric iron

    • Aluminium
    • An alloy such as constantan
    • Copper
    • Tungsten

  5. 5.A 2000 W heater is run for 3 hours. How much electrical energy does it use, in kilowatt hours? Answer with a number.

  6. 6.Resistors of 5 Ω, 8 Ω and 12 Ω are joined in series. What is the equivalent resistance, in ohms? Answer with a number.

  7. 7.Why can an electric bulb and an electric heater not sensibly be wired in series?

    • a) The heater would short out the bulb
    • b) The bulb would take the whole of the current and leave none for the heater
    • c) A series circuit cannot carry enough voltage for two devices
    • d) The current is the same throughout a series circuit, and the two need very different currents

  8. 8.A lamp of resistance 100 Ω is connected across a 220 V supply. What current does it draw, in amperes? Answer with a number.

Answer key — Year 11 Science — Electricity

  1. 1. 2
  2. 2. The current is the same through each resistor → Series; The potential differences across the resistors add up to the supply voltage → Series; When one component fails, nothing in the circuit works → Series; The potential difference is the same across each resistor → Parallel; The currents through the branches add up to the total current → Parallel; Each gadget can draw the current it needs → Parallel
  3. 3. b) Its wire melts under an unduly high current, breaking a circuit it sits in series with
  4. 4. Tungsten → Filaments of electric bulbs; Copper → Electrical transmission lines; Aluminium → Electrical transmission lines; An alloy such as constantan → Heating devices such as an electric iron
  5. 5. 6
  6. 6. 25
  7. 7. d) The current is the same throughout a series circuit, and the two need very different currents
  8. 8. 2.2