The resistance of a light-dependent resistor (LDR) is affected by the intensity of light falling on it. A student investigates this relationship by changing the distance between a small lamp and the LDR using the circuit shown below.
The student uses a voltmeter to measure the voltage across the LDR. Explain how the voltmeter should be connected to the circuit.
Explain how the student can work out the resistance of the LDR using this circuit.
The student places the LDR on an optical bench with a movable lamp to carry out the experiment.
The independent variable in this experiment is
A controlled variable in this experiment is
The diagram below shows how the student views a ruler to read the distance between the lamp and the LDR.
Suggest how the student can improve this technique to obtain a more accurate distance reading while using the same ruler.
The table shows the student's results.
| Distance (cm\text{cm}cm) | Resistance of LDR (Ω\OmegaΩ) |
|---|---|
| 10 | 180 |
| 20 | 620 |
| 30 | 1280 |
| 40 | 2150 |
| 50 | 3180 |
| 60 | 4300 |
Describe the relationship between the resistance of the LDR and the distance from the lamp.
