ELECTRICAL POWER
3 marks · NormalLook at these two electrical appliances:
| Appliance | Wire material | Wire resistance |
|---|---|---|
| Toaster | Nichrome (metal alloy) | High |
| Mains cable in wall | Copper | Low |
Explain why the heating element in a toaster uses a wire with high resistance, but the wires in a mains cable use low resistance copper.
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.
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The toaster's heating element uses a high-resistance wire so that electrical energy is transferred to heat when current passes through it. Copper is used in mains cables because its low resistance lets current pass easily, preventing the wire from heating up and making it safer.
Must show: heating element needs high resistance to generate heat, mains wire needs low resistance to avoid heat and energy loss, correct explanation for each
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Marking points
M1 (a) · 1 mark · Explain that high resistance in toaster causes heating effect.
M2 (a) · 1 mark · State that low resistance in copper mains wire prevents the wire from heating up.
A1 (a) · 1 mark · Correctly distinguish between functions of resistance in different appliances.
Worked solution
The toaster deliberately uses a high-resistance nichrome wire as a heating element, so when current passes through, it becomes hot and transfers heat to the bread. In contrast, the mains cable uses copper because of its low resistance, letting current flow easily with minimal energy converted to heat—this keeps the wire cool and safe during normal use.