An electronics technician investigated how the current in a test circuit varied with the resistance of a calibration rheostat (a variable resistor).
The table below shows the results of their investigation:
| Resistance of rheostat, RRR (Ω\OmegaΩ) | Current in circuit, III (A) |
|---|---|
| 20 | 0.60 |
| 30 | 0.40 |
| 40 | 0.30 |
| 60 | 0.20 |
| 80 | 0.15 |
The DC power supply had a power output of 1.80 W1.80\text{ W}1.80 W when the resistance of the rheostat was 80 Ω80\ \Omega80 Ω.
Determine the terminal potential difference across the power supply.
The technician concluded:
'The current in the circuit was inversely proportional to the resistance of the rheostat.'
Explain how the table of results shows that this conclusion is correct.
The technician then connected a bypass switch incorrectly, as shown in the circuit diagram below:
Explain how closing the switch would affect the current in the rheostat.
Current, potential difference and resistance Questions
Practise AQA GCSE Physics Current, potential difference and resistance with exam-style questions for Foundation and Higher tier. 82 questions covering Standard circuit diagram symbols, Electrical charge and current, Current, resistance and potential difference, and Resistors, matched to the AQA GCSE Physics (8463) specification and written in Paper 1 and Paper 2 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.