A manufacturer tests a thin metal heating wire for use in a battery-powered hand warmer.
| Time after the wire is switched on | Potential difference across the wire (V) | Current through the wire (A) |
|---|---|---|
| Immediately | 6.0 | 1.5 |
| After 30 seconds | 6.0 | 1.0 |
Calculate the resistance of the wire immediately after it is switched on and after 30 seconds.
Explain why the resistance of the wire changes during the 30 seconds.
The current through the wire must not be greater than 1.2 A during use. The manufacturer considers connecting the wire to a 9.0 V supply. Assume that the resistance of the wire is equal to its resistance after 30 seconds.
Calculate the current through the wire. Determine whether the wire is suitable for use with the 9.0 V supply. Give a reason for your answer.
82 exam-style questions on AQA GCSE Physics 2.1 Current, potential difference and resistance, covering 2.1.1 Standard circuit diagram symbols, 2.1.2 Electrical charge and current, 2.1.3 Current, resistance and potential difference, and 2.1.4 Resistors. Each one has a worked solution and a mark scheme showing where the marks go.