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Grade 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.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

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

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

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

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

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

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

  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.A device draws 0.25 A at a potential difference of 220 V. What is its power, in watts? Answer with a number.

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

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

  8. 8.A potential difference of 6 V across a resistor drives a current of 0.5 A through it. What is its resistance, in ohms? Answer with a number.

Answer key — Grade 10 Science — Electricity

  1. 1. Tungsten → Filaments of electric bulbs; Copper → Electrical transmission lines; Aluminum → Electrical transmission lines; An alloy such as constantan → Heating devices such as an electric iron
  2. 2. 25
  3. 3. b) The potential difference across a metallic wire is proportional to the current through it, at constant temperature
  4. 4. c) The current is the same throughout a series circuit, and the two need very different currents
  5. 5. 6
  6. 6. 55
  7. 7. d) It doubles
  8. 8. 12