In this experiment, you will measure the currents at two different points in the same circuit and investigate how the currents depend on the total resistance of the circuit. (i) Set up the circuit as shown in Fig. 1.1. There are crocodile clips at L, M and N. Place the crocodile clip at N so that the length $x$ from N to M is approximately 60 cm. (ii) Measure and record the value of $x$. $x$ = \_\_\_\_\_\_ (iii) Close the switch. (iv) Record the current $I_1$ given by…

Physics 9702/35 — October/November 2012

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 measure the currents at two different points in the same circuit and investigate how the currents depend on the total resistance of the circuit.

(a)

(i)

Set up the circuit as shown in Fig. 1.1.

Fig. 1.1

There are crocodile clips at L, M and N.

Place the crocodile clip at N so that the length $x$ from N to M is approximately 60 cm.

(ii)

Measure and record the value of $x$ .

$x$ = ______

(iii)

Close the switch.

(iv)

Record the current $I_1$ given by ammeter 1.

$I_1$ = ______

(v)

Record the current $I_2$ given by ammeter 2.

$I_2$ = ______

(vi)

Open the switch.

(b)

Change $x$ and repeat (a) until you have six sets of readings of $x$ , $I_1$ and $I_2$ where $x$ is in the range $0.200\ \text{m} \leq x \leq 0.800\ \text{m}$ .

Include values of $\frac{I_2}{I_1}$ and $\frac{1}{x}$ in your table.

(c)

(i)

Plot a graph of $\frac{I_2}{I_1}$ on the $y$ -axis against $\frac{1}{x}$ 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 = ______

(d)

The quantities $I_1$ , $I_2$ and $x$ are related by the equation

\frac{I_2}{I_1} = \frac{P}{x} + Q

where $P$ and $Q$ are constants.

Using your answers from (c)(iii), determine the values of $P$ and $Q$ .
Give appropriate units.

$P$ = ______
$Q$ = ______

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