O Level Physics 5054 Paper 41, May/June 2025

The student closes the switch. The readings of current $I_{\text{L}}$ and potential difference $V_{\text{L}}$ are shown in Fig. 1.2. Record the readings shown. $I_{\text{L}}=\text{............................................................ A}$ $V_{\text{L}}=\text{............................................................ V}$

The student opens the switch. Suggest why the switch is opened after the readings are recorded.

Use the equation $$R=\frac{V}{I}$$ to calculate the resistance $R_{\text{L}}$ of the lamp. Give your answer to 2 significant figures. $R_{\text{L}}=\text{...................................................... }\mathrm{\Omega }$

The student: • rearranges the circuit and connects a $10\mathrm{\Omega }$ resistor in series with the lamp • connects the voltmeter to measure the potential difference across the resistor and lamp combination. In the space below, draw the new circuit with the resistor added.

The reading on the voltmeter does not change. Fig. 1.3 shows the new current reading on the ammeter. This is current $I_{\text{C}}$. Record $I_{\text{C}}$. $I_{\text{C}}=\text{............................................................ A}$ Use the equation in (a)(iii) to find the resistance $R_{\text{C}}$ of the lamp and the resistor connected in series. $R_{\text{C}}=\text{............................................................ }\mathrm{\Omega }$

Theory states that the value of $R_{\text{L}}$ in the new circuit is given by: $$R_{\text{L}}=R_{\text{C}}-10$$ Calculate the resistance $R_{\text{L}}$ of the lamp. $R_{\text{L}}=\text{...................................................... }\mathrm{\Omega }$

State how the brightness of the lamp changes in the new circuit compared to the circuit shown in Fig. 1.1, and explain why. change in brightness of lamp ............................................................................................ ........................................................................................................................................... explanation ........................................................................................................................ ........................................................................................................................................... ...........................................................................................................................................

Draw a line from point A at an angle of ${30}^{\circ }$ in an anticlockwise direction from AB. This line should be more than $10\text{ cm}$ long. Label the end of the line as point C.

Mark a point D on the line AB, $4.0\text{ cm}$ from point A. Draw a line perpendicular to AB through point D. This line must also pass through the line AC that you have drawn in part (a)(i). Label, with an E, the point where the line through point D passes through AC.

The student: • places a plane mirror along the line AC with the reflective surface facing point B • arranges an illuminated slit so that a ray of light passes along the line DE. The ray reflects from the mirror. Draw a normal to line AC at point E.

Label the angle between DE and the normal you have drawn with a $\theta$. Measure and record angle $\theta$. $\theta ={\text{........................................................}}^{\circ }$

The student: • marks two points ${\text{P}}_1$ and ${\text{P}}_2$ on the reflected line • removes the mirror and draws the reflected line through points ${\text{P}}_1$ and ${\text{P}}_2$. Describe how points ${\text{P}}_1$ and ${\text{P}}_2$ are chosen to give as accurate a reflected line as possible.

The student repeats the procedure with a ray of light striking the mirror at a different angle. Fig. 2.2 shows a second line, labelled A'B'. On Fig. 2.2, draw a line from point A' at an angle of ${60}^{\circ }$ in an anticlockwise direction from line A'B'. The line should be more than $10\text{ cm}$ long. Label the end of the line with a C'.

Mark a point D' on the line A'B', $4.0\text{ cm}$ from point A'. Draw a line perpendicular to A'B' through point D'. This line must also pass through the line A'C'. Label the point where the line through point D' passes through A'C' with an E'. Draw a normal to line A'C' at point E'.

Label the angle between D'E' and the normal you have drawn with an $\alpha$. Explain one practical precaution that you take to ensure that the normal is accurately drawn.

Measure and record angle $\alpha$. $\alpha ={\text{........................................................}}^{\circ }$

Theory suggests that: $$\alpha =2\theta$$ State whether your results support this theory. Give a reason for your answer.

The student: • uses the $100{\text{ cm}}^3$ measuring cylinder to measure a volume $V=70{\text{ cm}}^3$ of water • places a finger under the hole at the bottom of the can and pours the water into the can from the measuring cylinder • removes the finger and, at the same time, starts the stopwatch • records the time $t_1$ when the volume of water collected in the measuring cylinder is $30{\text{ cm}}^3$ • stops the stopwatch. Fig. 3.2 shows the reading on the stopwatch at time $t_1$. Record $t_1$. $t_1=\text{....................................................... s}$

The student repeats (a)(i) and records the time $t_2$ shown in Fig. 3.3. Record $t_2$ and find the average time $t_{\text{av}}$ of $t_1$ and $t_2$. Give your answer to the nearest $0.1\text{ s}$. $t_2=\text{............................................................. s}$ $t_{\text{av}}=\text{............................................................. s}$

The average rate of flow $R$ is given by: $$R=\frac{30{\text{ cm}}^3}{t_{\text{av}}}$$ Calculate $R$ and give the unit of your answer. $R=\text{....................................... unit ...................}$

The student repeats (a)(i) and (a)(ii) for values of $V=100{\text{ cm}}^3$, $90{\text{ cm}}^3$, $80{\text{ cm}}^3$, $60{\text{ cm}}^3$ and $50{\text{ cm}}^3$. The volume of water collected in the measuring cylinder underneath the can is $30{\text{ cm}}^3$ for each value of $V$. The readings are shown in Table 3.1. In Table 3.1: • complete the headings, with units, in the top row of the table • add your readings from (a)(i) and (a)(ii) • calculate the average time for each set of readings. Table 3.1

On the grid provided in Fig. 3.4, plot a graph of $t_{\text{av}}$ on the $y$-axis against $V$ on the $x$-axis. You do not need to start your axes at $(0,0)$. Draw the curve of best fit.

Suggest why times $t_1$ and $t_2$ for values of $V$ below $50{\text{ cm}}^3$ are not measured.

On your graph, sketch the line you would expect to see if the small hole in the can is made slightly bigger. Label this line L.