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 use the readings from this circuit to determine both the resistance of the LDR and the electrical energy transferred by the LDR in a given time $t$.

The student varies the light intensity by changing the distance $d$ of a desktop lamp from the LDR in a darkroom.

• The orientation of the LDR relative to the lamp is kept constant.
• The ambient light in the room is kept constant by performing the experiment in a dark room with blacked-out windows.
• The student adjusts the variable resistor to keep the voltage across the LDR within safe limits to prevent damage.

The independent variable in this experiment is

• A the resistance of the LDR
• B the ambient light level
• C the distance from the lamp to the LDR
• D the current in the circuit

A controlled variable in this experiment is

• A the distance from the lamp to the LDR
• B the resistance of the LDR
• C the ambient light level
• D the power dissipated by the LDR

The diagram below shows how the student views a meter ruler to read the distance $d$ between the lamp and the LDR.

Draw on this

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.

Describe the relationship between the resistance of the LDR and the distance $d$.