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Class 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
    • Aluminium
    • Copper
    • An alloy such as constantan

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

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

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

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

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

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

  7. 7.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.

  8. 8.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 doubles
    • d) It halves

Answer key — Class 10 Science — Electricity

  1. 1. 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
  2. 2. c) The potential difference across a metallic wire is proportional to the current through it, at constant temperature
  3. 3. 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
  4. 4. 2
  5. 5. Electric current → Ampere; Potential difference → Volt; Resistance → Ohm; Electric power → Watt; Electrical energy sold commercially → Kilowatt hour
  6. 6. 2.2
  7. 7. 12
  8. 8. c) It doubles