Chapter 18 | Resistance, Power & Energy

Resistance, Ohm’s Law, Electrical Power & Energy

Build evidence from meter readings, test proportionality, compare component characteristics, and calculate energy use and cost.

Cambridge IGCSE Physics
Core + Supplement

Supply setting 2.0 V

Test resistor 10 Ω

V / V	I / A	R = V/I / Ω
Keep R fixed and record five different supply settings.

Wire length, L 1.00 m

Wire diameter 0.50 mm

Applied potential difference 2.0 V

Potential difference 12 V

Current 2.0 A

Operating time 60 s

Component

Appliance

Hours per day 3.0 h

Number of days 30 days

Tariff 0.18 SAR/kWh

1. A resistor has 6.0 V across it and a current of 0.50 A. Find R.

2. What must be kept constant when testing Ohm’s law for a metallic conductor?

3. If the length of a wire doubles while area and material stay constant, R…

4. Which component has a curved, symmetrical I–V graph because it heats up?

5. Calculate the power when V = 12 V and I = 3.0 A.

6. A 2.0 kW heater runs for 3.0 h. Find the energy used.

kWh

7. That 6.0 kWh costs 0.20 SAR per kWh. Find the cost.

SAR