The student measures the room temperature $\theta_R$. Fig. 2.2 shows the thermometer. Enter the reading of $\theta_R$ on the answer line. $\theta_R =$ [BLANK] $^\circ\text{C}$.
Enter the potential difference $V_{XY}$ for the thermistor at room temperature $\theta_R$ in Table 2.1.
Re-draw the circuit shown in Fig. 2.1 on page 5 so that the voltmeter is connected to measure the potential difference across the $220\,\Omega$ resistor.
Explain why the student waits for 30 s before measuring the temperature of the hot water.
Explain why the student stirs the water before reading the temperature of the hot water from the thermometer.
Study the data in Table 2.1. Compare the reading for the potential difference across the thermistor $V_{XY}$ at room temperature $\theta_R$ with the reading for the potential difference across the thermistor $V_{XY}$ at the temperature of the hot water $\theta_H$. Suggest what causes the difference in the readings.
The current $I$ in the circuit is found using the equation $I = \frac{V_{YZ}}{R}$, where $R = 220\,\Omega$. Use the measurements recorded in Table 2.1 to calculate the current $I$ at room temperature $\theta_R$ and at the temperature of the hot water $\theta_H$. Enter your answers in Table 2.1.
The resistance $R_T$ of the thermistor is found using the equation $R_T = \frac{V_{XY}}{I}$. Use the data in Table 2.1 to calculate $R_T$ at room temperature $\theta_R$ and at the temperature of the hot water $\theta_H$.
Calculate $\alpha$, the average change in thermistor resistance per degree Celsius, for the thermistor as its temperature rises from room temperature $\theta_R$ to the temperature of the hot water $\theta_H$. Use the equation $\alpha = \frac{\text{change in resistance of thermistor}}{\text{change in temperature}}$. Give your answer to 2 significant figures.