Physics 9702/33 — October/November 2013

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

Q1Manipulation, Measurement and ObservationPresentation of Data and ObservationsAnalysis, Conclusions and EvaluationFree sample

In this experiment, you will determine the resistivity of a metal in the form of a wire.

(a)

(i)

Measure and record the diameter $d$ of the short sample of wire that is attached to the card. You may remove the wire from the card.

$d$ = ______

(ii)

Calculate the cross-sectional area $A$ of the wire, in $\text{m}^2$ , using the formula

A = \frac{\pi d^2}{4}

$A$ = ______ $\text{m}^2$

(b)

(i)

Use the wire attached to the metre rule, one of the voltmeters and one of the resistors to set up the partial circuit shown in Fig. 1.1.

Fig. 1.1

There are two crocodile clips, one labelled K and the other labelled L.
Place K and L so that the distance $l$ between them is approximately 30 cm.

(ii)

Measure and record the distance $l$ between K and L.

$l$ = ______ $\text{m}$

(iii)

Use the other resistor and the other voltmeter to complete the circuit shown in Fig. 1.2.

Fig. 1.2

(iv)

Place the crocodile clip M at a distance $l$ from L.
The value of $l$ should be the same as in (b)(ii).

(c)

(i)

Switch on the power supply.

(ii)

Record the voltmeter readings $V_1$ and $V_2$ as shown in Fig. 1.2.

$V_1$ = ______ $\text{V}$
$V_2$ = ______ $\text{V}$

(iii)

Switch off the power supply.

(d)

Change $l$ and repeat (b)(ii), (b)(iv) and (c) until you have six sets of readings of $l$ , $V_1$ and $V_2$ . For each set of readings, distances KL and LM should both be $l$ .

Include values of $\frac{V_1}{V_2}$ in your table.

10M

(e)

(i)

Plot a graph of $\frac{V_1}{V_2}$ on the $y$ -axis against $l$ 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 = ______

(f)

The quantities $V_1$ , $V_2$ and $l$ are related by the equation

\frac{V_1}{V_2} = Pl + Q

where $P$ and $Q$ are constants.

(i)

Use your answers in (e)(iii) to determine values for $P$ and $Q$ .

$P$ = ______ $\text{m}^{-1}$
$Q$ = ______

(ii)

The resistivity $\rho$ of the material of the wire, in $\Omega\ \text{m}$ , can be found using the relationship

\rho = PAR

where $R = 10\ \Omega$ .

Use your answers in (a)(ii) and (f)(i) to calculate a value for $\rho$ .

$\rho$ = ______ $\Omega\ \text{m}$

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