Question Constellation Sign up for free AQA · GCSE · Combined Science · Higher
Comparing low- and high-resistance cables
A hybrid car has an electric motor powered by a battery and is charged from the mains electricity supply.
The cable used to connect the car to the mains electricity supply has a low resistance.
Explain why it is better to use a cable with a low resistance than to use a cable with a high resistance.
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Marking points
- 1 Explain that a low-resistance cable has a lower potential difference across it, or lower power/energy dissipation, than a high-resistance cable.
- 2 Link this to the cable being more efficient or not getting as hot.
- 3 Alternatively, explain that lower resistance gives a greater current for the same potential difference.
- 4 Link the greater current to the car battery charging faster.
Full-mark answer
A low-resistance cable has less potential difference across it, so less energy is dissipated in the cable and the charging is more efficient.
Why this answer loses marks
Because low resistance is safer.
This does not explain the credited electrical effect or the efficiency/charging benefit.