Success Homeschool

Year 12 Science · Electric circuits and power

Name: ______________________

Date: ____________

1. What is the unit of resistance?
- ☐ (a) Ampere
- ☐ (b) Volt
- ☐ (c) Ohm
- ☐ (d) Watt
2. A current of 2 A flows through a 5 Ω resistor. What is the potential difference across it?
- ☐ (a) 10 V
- ☐ (b) 2.5 V
- ☐ (c) 0.4 V
- ☐ (d) 7 V
3. Two 10 Ω resistors are connected in parallel. What is the total resistance?
- ☐ (a) 20 Ω
- ☐ (b) 10 Ω
- ☐ (c) 0.2 Ω
- ☐ (d) 5 Ω
4. Why are household appliances connected in parallel?
- ☐ (a) So they share the voltage equally
- ☐ (b) So each receives the full supply voltage and can be switched independently
- ☐ (c) So the same current flows through each
- ☐ (d) So the total resistance increases
5. A 60 W device runs for 5 hours. How much energy does it use?
- ☐ (a) 12 kWh
- ☐ (b) 0.3 kWh
- ☐ (c) 3 kWh
- ☐ (d) 300 kWh
6. Resistors of 4 Ω, 6 Ω and 10 Ω are in series. What is the total resistance in ohms? (number)
7. A 1150 W toaster runs on 230 V. What current does it draw in amperes? (number)
8. A 3 A current flows through a 4 Ω resistor. What power is dissipated in watts? (number)

Answer sheet

1. Ohm — Resistance is measured in ohms (Ω).
2. 10 V — V = IR = 2 × 5 = 10 V.
3. 5 Ω — 1/R = 1/10 + 1/10 = 2/10, so R = 5 Ω.
4. So each receives the full supply voltage and can be switched independently — Parallel wiring gives each appliance the full voltage and independent control.
5. 0.3 kWh — E = 0.06 kW × 5 h = 0.3 kWh.
6. 20 — 4 + 6 + 10 = 20 Ω.
7. 5 — I = P ÷ V = 1150 ÷ 230 = 5 A.
8. 36 — P = I²R = 3² × 4 = 9 × 4 = 36 W.