Mains Electricity
3 marks · NormalAn electric heater is rated at 2 kW and is connected to a 230 V mains supply. It is used for 30 minutes.
Explain how the heater uses the heating effect of an electric current to warm up a room.
Calculate the total energy transferred by the heater during this time.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) Current flows through a high resistance wire in the heater, causing the wire to become hot and transfer energy as heat to warm up the air in the room. · must show current through resistance, heats up
(b) 3,600,000 J
Common mistakes: Misses resistance role in heating; Incorrect conversion of kW to W
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · States current flows through a resistor/high resistance wire
B2 (a) · 1 mark · Explains this causes it to heat up and warm the room
A1 (b) · 1 mark · Correct calculation: 2000 × 1800 = 3,600,000 J
Worked solution
a) When current passes through a high resistance wire (the heating element), energy is transferred to the wire as heat. This heat is released into the air to warm the room.
b) 30 minutes = 1800 s. Energy