A student sets up an electrical circuit containing a DC power source, a slide-wire rheostat (which acts as a variable resistor), a digital ammeter, and a small electrical heating coil connected in series.
Describe how a voltmeter should be connected to the circuit to measure the potential difference across the heating coil.
The student records the potential difference across the heating coil and the corresponding current flowing through it in the table below:
| Potential difference | Current (A) |
|---|---|
| 2.0 | 0.50 |
| 4.0 | 0.800 |
| 6.0 | 1.00 |
| 8.0 | 1.15 |
| 10.0 | 1.25 |
There are two mistakes in this results table. Identify these two mistakes and state how they should be corrected.
Use the equation:
potential difference=current×resistance \text{potential difference} = \text{current} \times \text{resistance} potential difference=current×resistanceto calculate the resistance of the heating coil when the potential difference is 6.0 V6.0\text{ V}6.0 V.
Describe the relationship between current and potential difference for the heating coil shown by the data in the table.
Explain how the student could adapt the experiment to investigate the resistance of a fixed resistor rather than a heating coil.
Explain how and why the current–potential difference graph would look different for a fixed resistor at a constant temperature compared to the heating coil.
42 exam-style questions on OCR GCSE Physics Simple circuits. Each one has a worked solution and a mark scheme showing where the marks go.