A student sets up a circuit consisting of a DC power supply, a variable resistor, an ammeter, and a filament lamp connected in series.
Describe how a voltmeter should be connected to the circuit to measure the potential difference across the filament lamp.
The student records the potential difference across the lamp and the corresponding current flowing through it in the table below:
| Potential difference (V) | Current |
|---|---|
| 1.5 | 0.500 |
| 3.0 | 0.80 |
| 4.5 | 1.00 |
| 6.0 | 1.15 |
| 7.5 | 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×resistance
to calculate the resistance of the lamp when the potential difference is 4.5 V4.5\text{ V}4.5 V.
Describe the relationship between current and potential difference for a filament lamp 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 filament lamp.
Explain how and why the current–potential difference graph would look different for a fixed resistor at a constant temperature compared to the filament lamp.