In this experiment, you will investigate how the current in a circuit changes as the resistance of the circuit is changed. (i) Set up the apparatus as shown in Fig. 1.1. (ii) Measure and record the length $L$ of the shorter wire. $L$ = \_\_\_\_\_\_ (i) Complete the circuit as shown in Fig. 1.2. Each crocodile clip should be attached to a wire at the same distance $x$ from the end of the wire, as shown in Fig. 1.2. (ii) Measure and record the distance $x$. $x$ = \_\_\_\_\_\_…

Physics 9702/35 — May/June 2016

Cambridge AS Level · Advanced Practical Skills · worked solutions for every part, with the mark scheme

questions

marks

120

minutes

Topics Manipulation, Measurement and Observation · Presentation of Data and Observations · Analysis, Conclusions and Evaluation

Q120MManipulation, Measurement and ObservationPresentation of Data and ObservationsAnalysis, Conclusions and EvaluationFree sample

In this experiment, you will investigate how the current in a circuit changes as the resistance of the circuit is changed.

(a)

(i)

Set up the apparatus as shown in Fig. 1.1.

Fig. 1.1

(ii)

Measure and record the length $L$ of the shorter wire.

$L$ = ______

(b)

(i)

Complete the circuit as shown in Fig. 1.2.

Fig. 1.2

Each crocodile clip should be attached to a wire at the same distance $x$ from the end of the wire, as shown in Fig. 1.2.

(ii)

Measure and record the distance $x$ .

$x$ = ______

(iii)

Close the switch.

(iv)

Record the ammeter reading $I$ .

$I$ = ______

(v)

Open the switch.

(c)

Change $x$ and repeat (b) until you have six sets of readings of $x$ and $I$ .

Include values of $\frac{1}{I}$ in your table.

(d)

(i)

Plot a graph of $\frac{1}{I}$ on the $y$ -axis against $x$ on the $x$ -axis.

(ii)

Draw the straight line of best fit.

(iii)

Determine the gradient and $y$ -intercept of this line.

gradient = ______
$y$ -intercept = ______

(e)

The quantities $I$ and $x$ are related by the equation

\frac{1}{I} = -Px + Q

where $P$ and $Q$ are constants.

Using your answers in (d)(iii), determine values for $P$ and $Q$ .
Give appropriate units.

$P$ = ______
$Q$ = ______

(f)

(i)

The e.m.f. $E$ of the d.c. power supply is given on the card.
Record $E$ .

$E$ = ______ $\text{V}$

(ii)

Theory suggests that

Q = \frac{R}{E} + \frac{3PL}{2}

where $R$ is the resistance of the resistor.

Use values in (a)(ii), (e) and (f)(i) to determine the value of $R$ .

$R$ = ______ $\Omega$

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