A student investigates how the current in a thermistor depends upon temperature. She sets up the circuit shown in Fig. 1.1. - She pours hot water into the beaker. - She stirs the water, measures its temperature and reads the ammeter. - She records the values of temperature and current in the table of Fig. 1.2. - She repeats these readings at $10^\circ\text{C}$ intervals, as the water cools, until the water reaches room temperature. - She records all her readings in the…

Physics 5054/42 — October/November 2018

Cambridge O-Level · Alternative to Practical · worked solutions for every part, with the mark scheme

questions

marks

minutes

Topics Use of Techniques, Apparatus and Materials · Observations and Measurements · Experimental Contexts · Analysis, Conclusions and Evaluation · Planning Experiments and Investigations

Q1Observations and MeasurementsExperimental ContextsUse of Techniques, Apparatus and MaterialsAnalysis, Conclusions and EvaluationPlanning Experiments and InvestigationsFree sample

A student investigates how the current in a thermistor depends upon temperature.

She sets up the circuit shown in Fig. 1.1.

Fig. 1.1

She pours hot water into the beaker.
She stirs the water, measures its temperature and reads the ammeter.
She records the values of temperature and current in the table of Fig. 1.2.
She repeats these readings at $10^\circ\text{C}$ intervals, as the water cools, until the water reaches room temperature.
She records all her readings in the table, as shown in Fig. 1.2.

Fig. 1.2

temperature $\theta / ^\circ\text{C}$	current $I / \text{mA}$
80	2.90
70	2.30
60	1.75
50	1.20
40
30	0.60
20	0.45

Fig. 1.3 shows the ammeter reading when the temperature of the water is $40^\circ\text{C}$ .

Fig. 1.3

(a)

(i)

Read the ammeter and record the missing value of current in the table of Fig. 1.2.

(ii)

State why the student stirs the water before taking a temperature reading.

(b)

On Fig. 1.4, plot a graph of $I$ on the y-axis against $\theta$ on the x-axis. Start both axes from the origin.

Draw the smooth curve of best fit.

Fig. 1.4

(c)

(i)

Extend your curve to predict the current for the temperature of $0^\circ\text{C}$ .

current at $0^\circ\text{C}$ = ______ $\text{mA}$

(ii)

Suggest how the student can modify her investigation to check the prediction made in (c)(i).

(d)

(i)

Use your graph to estimate the current $I$ when the temperature of the water is $75^\circ\text{C}$ .

$I$ = ______ $\text{mA}$

(ii)

The voltage $V$ of the power supply is 5.0 V.

Use the equation

R = \frac{V}{I}

to calculate the resistance $R$ of the thermistor at $75^\circ\text{C}$ .

$R$ = ______ $\Omega$

(e)

(i)

Describe the relationship between current and temperature for the thermistor, shown by your graph.

(ii)

Deduce the relationship between resistance and temperature for the thermistor.

The rest of this paper

3 more questions

Q2Observations and Measurements · Experimental Contexts · Use of Techniques, Apparatus and Materials6M
Q3Experimental Contexts · Analysis, Conclusions and Evaluation · Observations and Measurements · Use of Techniques, Apparatus and Materials6M
Q4Use of Techniques, Apparatus and Materials · Analysis, Conclusions and Evaluation4M

Loading the full paper…