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Year 10 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.Which statement is Ohm's law as the chapter states it?

    • a) The potential difference across a metallic wire is proportional to its length
    • b) The current through a metallic wire is proportional to its resistance
    • c) The potential difference across a metallic wire is proportional to the current through it, at constant temperature
    • d) The resistance of a metallic wire is proportional to the current through it

  2. 2.A wire is replaced by another of the same material and thickness but twice the length. What happens to its resistance?

    • a) It falls to a quarter
    • b) It halves
    • c) It stays the same
    • d) It doubles

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

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

  4. 4.A circuit is drawn below: a cell on the left, a resistor along the top, and two round instruments wired into it. Tap the one that is connected across the resistor rather than in the loop with it.

    Write the number of the part.

    12

  5. 5.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 lowers the resistance of the circuit so less current flows
    • d) It stores charge until the current returns to normal

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

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

  8. 8.Match each electrical quantity to its SI unit.

    • Electric current
    • Potential difference
    • Resistance
    • Electric power
    • Electrical energy sold commercially
    • Watt
    • Volt
    • Ampere
    • Ohm
    • Kilowatt hour

Answer key — Year 10 Science — Electricity

  1. 1. c) The potential difference across a metallic wire is proportional to the current through it, at constant temperature
  2. 2. d) It doubles
  3. 3. a) The current is the same throughout a series circuit, and the two need very different currents
  4. 4. 2 — The instrument across the resistor
  5. 5. b) Its wire melts under an unduly high current, breaking a circuit it sits in series with
  6. 6. 2
  7. 7. 25
  8. 8. Electric current → Ampere; Potential difference → Volt; Resistance → Ohm; Electric power → Watt; Electrical energy sold commercially → Kilowatt hour