A student investigates the effect of varying the amount of light reaching a light-dependent resistor (LDR).
She sets up the apparatus as shown in Fig. 1.1.
Fig. 1.2 shows the reading on the voltmeter when the light source is turned on and the switch is closed.
Record the reading on the voltmeter on the answer line and in the first row of Table 1.1.
voltmeter reading = ...................................... V
The student uses a syringe to add 2 cm³ of a coloured liquid to the water in the beaker and stirs the mixture.
Explain why the student must stir the two liquids together.
The student continues to add 2 cm³ of coloured liquid to the water at a time, recording each new voltmeter reading in Table 1.1.
| volume of coloured liquid / cm³ | voltmeter reading / V |
|---|---|
| 0 | .......... |
| 2 | 2.4 |
| 4 | 2.2 |
| 6 | 1.8 |
| 8 | 1.6 |
| 10 | 1.5 |
| 12 | 1.4 |
On Fig. 1.3, plot a graph of the voltmeter reading against the volume of coloured liquid.
Draw the best-fit curve.
Draw a tangent to the curve at 5 cm³.
Calculate the gradient of the tangent.
Show your working and indicate on the graph the values that you use.
gradient = ......................................
Describe one precaution taken to ensure that the reading from a voltmeter is accurate.
Another student performs the same experiment. He calculates a gradient which is slightly different to the value you obtained in (c)(ii).
Suggest two variables that are difficult to control that may result in different gradients.
5054/04/SP/23Cambridge O Level Physics 5054 · Specimen 2023 · Paper 4 · Question 1