Marking Scheme: Electricity Quiz

This is the marking scheme for quiz: P5 - Electricity Quiz
Topic guide: P5 - Electricity

Section A: Multiple Choice

  1. c) Electrons (1)
  2. a) $1.6 \times 10^{-19}\text{ C}$ (1)
  3. b) Positive to negative (1)
  4. d) Increasing the length (1)
  5. c) Current (1)
  6. b) Positive terminal to negative terminal (1)

Section B: Short Answer

  1. Charging by Friction (3 marks)

    • Rubbing two materials (e.g., balloon and hair) causes electron transfer (1).
    • One material loses electrons and becomes positive; the other gains electrons and becomes negative (1).
    • Example: Electrons move from hair to balloon (or vice versa), creating a static charge (1).

  2. Conduction vs Induction (4 marks)

    • Conduction: Requires direct contact; excess charge moves through solid connection until equilibrium (2).
    • Induction: No contact required; nearby charged object causes polarization/charge separation within the target object (2).

  3. Metals vs Non-metals (3 marks)

    • Metals have a “free electron sea” model (1).
    • Some electron shells have free electrons available that are not bound to a specific nucleus (1).
    • This high number of mobile carriers allows for easy conduction of charge (1).

  4. Current Calculation (3 marks)

    • Formula: $I = Q / t$ (1)
    • Substitution: $I = 12\text{ C} / 4\text{ s}$ (1)
    • Answer: $3\text{ A}$ (1)

  5. Ohm’s Law (3 marks)

    • Definition: Voltage is proportional to current for a constant resistance (1).
    • Formula: $V = I \times R$ or $R = V / I$ (2).

  6. Power Calculation (4 marks)

    • a) $V = I \times R = 5\text{ A} \times 20\ \Omega = 100\text{ V}$ (2)
    • b) $P = I^2 \times R = 5^2 \times 20 = 25 \times 20 = 500\text{ W}$ (OR $P = V \times I = 100 \times 5 = 500\text{ W}$) (2)

  7. Temperature and Resistance (3 marks)

    • Effect: Resistance increases as temperature increases (1).
    • Reason: Higher temperature increases atomic vibration (1).
    • This leads to more collisions between electrons and the lattice structure, opposing flow (1).

  8. EMF vs PD (3 marks)

    • EMF: Work done by source to move charge around a circuit / voltage between terminals (1).
    • PD: Voltage between two specific points on a circuit (1).
    • Difference: EMF is the total potential provided by the source; PD is the energy used across a specific component (1).