A student investigates how the resistance of a light-dependent resistor (LDR) changes as a lamp is moved further away from it.
The LDR is connected in series with a battery and an ammeter. A voltmeter is connected across the LDR. The student measures the distance between the lamp and the LDR with a metre rule.
State the independent variable in this investigation.
Give two variables that the student should control.
When the lamp is 20 cm from the LDR, the voltmeter reads 6.0 V and the ammeter reads 1.5 mA.
Calculate the resistance of the LDR.
Give your answer in kΩ\text{k}\OmegakΩ.
The student moves the lamp further away from the LDR. The potential difference across the LDR stays the same.
Explain why the reading on the ammeter decreases.
81 exam-style questions on Edexcel GCSE Physics 10.2 Resistance, covering 10.2.1 Current in a circuit and conservation at junctions, 10.2.2 Resistance and variable resistors, 10.2.3 Series and parallel resistance, 10.2.4 I–V characteristics of components, and 10.2.5 LDRs and thermistors. Each one has a worked solution and a mark scheme showing where the marks go.