O Level Physics 5054 Paper 42, May/June 2024

The student connects a voltmeter into the circuit to measure the potential difference (p.d.) across the diode. On Fig. 1.1, draw the symbol for a voltmeter connected to measure the p.d. across the diode.

The student: • uses a connecting lead to connect the terminals X and Y together • closes the switch • records the voltmeter reading $V$ • records the ammeter reading $I$ • opens the switch and removes the connecting lead. Fig. 1.2 shows the readings on the voltmeter and the ammeter. Record the readings shown in Fig. 1.2 in the top row of Table 1.1.

Calculate the resistance $R$ of the diode using the equation: $$R=\frac{V}{I}$$ Record your answer in the top row of Table 1.1 to an appropriate number of significant figures.

The student: • connects a $3.3\mathrm{\Omega }$ resistor between terminals X and Y • closes the switch • records the voltmeter reading $V$ in Table 1.1 • records the ammeter reading $I$ in Table 1.1 • opens the switch and removes the $3.3\mathrm{\Omega }$ resistor • repeats this procedure for resistors of $6.8\mathrm{\Omega }$ and $10\mathrm{\Omega }$. Complete Table 1.1 by inserting the missing values.

As the resistance between terminals X and Y is changed, the current in the circuit changes. Examine the results shown in Table 1.1. Describe how the change in current affects: the voltage across the diode

the resistance of the diode.

A student sets up a circuit using the diagram shown in Fig. 1.1. The student finds that, when the connecting lead is connected across the terminals X and Y and the switch is closed, the ammeter does not give a reading. The ammeter is not broken. Suggest the error that the student has made while assembling the circuit.

The student: • arranges a test-tube as shown in Fig. 2.1 • pours $200{\mathrm{c}\mathrm{m}}^3$ of cold water into a beaker • pours hot water into the test-tube until it is approximately one-third full • lowers the test-tube into the beaker of cold water until the level of the hot water in the test-tube is below the level of the cold water in the beaker as shown in Fig. 2.2 • places a thermometer into the test-tube • waits for approximately $30\mathrm{s}$ before measuring the temperature and starting a stop-watch. The student measures the temperature $\theta$ of the hot water in the test-tube. The thermometer reading is shown in Fig. 2.3 Read the thermometer and record the temperature in Table 2.1 at time $t=0$.

The student measures the temperature $\theta$ of the hot water every $30\mathrm{s}$ for a further $180\mathrm{s}$. The readings are shown in Table 2.1. Complete the column headings by adding appropriate units.

Complete the time column.

Describe in detail one precaution that the student must take to make sure that the temperature measurements are as accurate as possible.

The student repeats the procedure in (a) and (b) but with $200{\mathrm{c}\mathrm{m}}^3$ of warm water instead of cold water in the beaker as shown in Fig. 2.4. The student's readings with warm water are shown in Table 2.1. One of the student's readings for warm water recorded in Table 2.1 is anomalous. Identify the anomalous temperature reading and explain how you decided that the reading is anomalous.

Use the temperature readings in Table 2.1 to calculate the temperature decrease of the hot water in the test-tube after cooling for $180\mathrm{s}$ in both the beaker of cold water and the beaker of warm water.

Use your answers to (d)(ii) to decide how the temperature of the water in the beaker affects the rate of cooling of hot water in the test-tube. State your conclusion.

Suggest one improvement to the experimental procedure described in (a) and (b) that allows a more valid comparison to be made between the two rates of cooling.

Take readings from the rule and use them to determine the position of the centre of the $50\mathrm{g}$ mass on the rule.

Calculate the distance $d$ from the centre of the $50\mathrm{g}$ mass to the $50.0\mathrm{c}\mathrm{m}$ mark on the rule. Record your answer on the answer line and in Table 3.1 on page 12.

Calculate the value of $\frac{1000}{d}$. Record your answer on the answer line and in Table 3.1 on page 12.

It is difficult to balance the rule exactly. Describe a technique that the student uses to make sure that the value of $d$ is as accurate as possible.

The student repeats the procedure in (a) for values of mass $m$ from $60\mathrm{g}$ to $100\mathrm{g}$ and records all the readings in Table 3.1. On the grid provided in Fig. 3.3 on page 13, plot a graph of $m$ on the $y$-axis against $\frac{1000}{d}$ on the $x$-axis. The axes do not need to start from the origin $(0,0)$. Draw the straight line of best fit.

Calculate the gradient $G$ of your line. Show all working and indicate on the graph the values you use.

The mass $M$ of the load fixed to the rule can be determined using the equation: $$M=22.2\times G$$ Use your value of $G$ from (d)(i) to calculate the mass $M$ of the load fixed to the rule.

Suggest why this method of determining the mass $M$ of the fixed load is unsuitable if a movable load of mass $m=40\mathrm{g}$ is used.