O Level Physics 5054 Paper 42, Oct/Nov 2025

Draw a diagram of the circuit arrangement, using the correct symbols for the components in the circuit. Choose from the symbols shown in Fig. 1.1. Fig. 1.1

The student: • closes the switch • connects a voltmeter across the LDR • records the voltmeter reading $V_1$ • opens the switch. On your circuit in (a), draw a voltmeter connected across the LDR to measure the potential difference (p.d.) across the LDR. Use the circuit symbol for a voltmeter.

The voltmeter reading $V_1$ is shown in Fig. 1.2. Fig. 1.2 Record the voltmeter reading $V_1$. $V_1=$ ...................................................... V

Suggest why the switch is opened after the voltmeter reading has been recorded.

The student: • disconnects the voltmeter • reconnects the voltmeter across the $560\mathrm{\Omega }$ resistor • closes the switch • records the voltmeter reading $V_2$ • opens the switch. The student measures $V_2$ as $2.18\mathrm{V}$. The current $I$ in the circuit is calculated using the equation: $$I=\frac{V_2}{R}$$ where $R=560\mathrm{\Omega }$. Calculate the current $I$. $I=$ .......................................................A

Use your answers from (b)(ii) and (c)(i) to calculate the resistance $R_{\mathrm{L}\mathrm{D}\mathrm{R}}$ of the LDR under normal lighting conditions, using the equation shown. $$R_{\mathrm{L}\mathrm{D}\mathrm{R}}=\frac{V_1}{I}$$ $R_{\mathrm{L}\mathrm{D}\mathrm{R}}=$ ...................................................... $\mathrm{\Omega }$

The student: • disconnects the voltmeter from across the $560\mathrm{\Omega }$ resistor • reconnects the voltmeter across the LDR • places a piece of card on top of the LDR to prevent light from reaching the LDR • closes the switch • records the voltmeter reading $V_3$ • opens the switch. The student measures $V_3$ as $1.94\mathrm{V}$. Compare $V_1$, measured under normal lighting conditions in (b)(ii), with $V_3$, measured in the dark. Suggest what causes the change in the readings as the intensity of the light reaching the LDR decreases.

The student: • holds the card horizontally $50\mathrm{c}\mathrm{m}$ above the LDR • slowly moves the card towards the LDR until it rests on top of the LDR • observes the readings on the voltmeter across the LDR as the card is moved. Table 1.1 shows the voltmeter readings as the distance $d$ between the card and the LDR decreases. Table 1.1 Describe the relationship between $d$ and $V$ shown by these readings.

procedure The student: • adjusts the distance $d$ between the white card attached to the thermometer bulb and the lamp until it is approximately $1\mathrm{c}\mathrm{m}$ • records, in Table 2.1, the initial temperature ${\theta }_{\mathrm{W}}$ recorded by the thermometer. The thermometer is shown in Fig. 2.2. Fig. 2.2 Record ${\theta }_{\mathrm{W}}$ in Table 2.1 at time $t=0$.

The student: • switches on the lamp and, at the same time, starts the stop-watch • records, in Table 2.1, the reading on the thermometer every $60\mathrm{s}$ for 5 minutes • switches off the lamp. The student’s results are shown in Table 2.1. Table 2.1 Complete Table 2.1 by completing the time column.

The student • removes the thermometer from the clamp • replaces it with a thermometer with a black card attached to its bulb • repeats the procedure in (a) and records temperatures ${\theta }_{\mathrm{B}}$. Determine the temperature increase $\mathrm{\Delta }\theta$ between $t=0$ and $t=300\mathrm{s}$ for each card. $\mathrm{\Delta }\theta$ for white card = .......................................................... °C $\mathrm{\Delta }\theta$ for black card = .......................................................... °C

Calculate the rate of increase of temperature of each card. Use the equation: $$\text{rate of temperature increase}=\frac{\mathrm{\Delta }\theta }{t}$$ Include the unit in your answer. rate of temperature increase of white card = ................................. unit ............... rate of temperature increase of black card = ................................. unit ...............

Use your answers to (b)(ii) to reach a conclusion which compares the absorption of thermal radiation by the two different cards. State your conclusion.

A student suggests that the rate of temperature increase is greater at the start of the experiment than at the end. State if the results for the black card support this suggestion. Justify your answer by referring to the results. statement .......................................................................................................................... justification ........................................................................................................................ ........................................................................................................................................... ...........................................................................................................................................

State two variables that are controlled in this experiment so that the comparison between the absorbing properties of white and black surfaces is valid. controlled variable 1 ................................................................................................................. ................................................................................................................................................... controlled variable 2 ................................................................................................................. ...................................................................................................................................................

The student: • places the metre rule on a pivot • places a mass $m=20\mathrm{g}$ on the metre rule with its centre at the $5.0\mathrm{c}\mathrm{m}$ mark • adjusts the position of the metre rule on the pivot until the metre rule is as close to balance as possible. Fig. 3.1 shows the balanced metre rule. Fig. 3.2 shows the position of the pivot under the metre rule when the metre rule is balanced. Fig. 3.2 Read the position of the pivot on the metre rule when the metre rule is balanced. Record the reading in centimetres to the nearest millimetre in Table 3.1 on page 10.

Calculate and record, in Table 3.1 on page 10: 1 the distance $a$ between the $5.0\mathrm{c}\mathrm{m}$ mark and the pivot 2 the distance $b$ between the pivot and the $50.0\mathrm{c}\mathrm{m}$ mark.

The student repeats the procedure in (a) for $m=40\mathrm{g}$, $60\mathrm{g}$, $80\mathrm{g}$ and $100\mathrm{g}$. The results are shown in Table 3.1. Describe how the student makes sure that the centre of each mass placed on the metre rule is directly above the $5.0\mathrm{c}\mathrm{m}$ mark.

Calculate the ratio $r=\frac{b}{a}$ for $m=20\mathrm{g}$. Record, in Table 3.1, your answer to two significant figures.

On the grid provided in Fig. 3.3 on page 11, plot a graph of $r$ on the $y$-axis against $m$ on the $x$-axis. Start from the origin (0, 0). Draw the straight line of best fit.

Calculate the gradient $G$ of your graph. Show clearly on the graph how you obtained the numbers you use for your calculation. $G=$ .........................................................

The mass $M$ of the metre rule in grams is given by the equation: $$M=\frac{1}{G}$$ Determine the mass of the metre rule to the nearest gram. $M=$ .......................................................g

Name a piece of apparatus that the student can use to measure the mass of the metre rule directly.

A student says that the centre of mass of the metre rule is at the $50.0\mathrm{c}\mathrm{m}$ mark. Describe how you use the apparatus provided to check that this statement is correct.