Physics 9702/31 — May/June 2015

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 investigate how the current in a circuit varies as the resistance of the circuit is changed.

(a)

(i)

You have been provided with a length of bare wire and two crocodile clips which have small screws on them. Connect the wire between the crocodile clips using the screws as shown in Fig. 1.1.

The length $w$ of wire between the screws should be approximately $50\text{ cm}$ . The screws should be tightened using the screwdriver.

Fig. 1.1

(ii)

Measure and record $w$ .

$w$ = ______

(b)

(i)

Set up the circuit as shown in Fig. 1.2.

Fig. 1.2

(ii)

Close the switch.

(iii)

Record the ammeter reading $I_A$ .

$I_A$ = ______

(iv)

Open the switch.

(c)

(i)

Move the crocodile clip to set up the circuit as shown in Fig. 1.3.

Fig. 1.3

(ii)

Close the switch.

(iii)

Record the ammeter reading $I_B$ .

$I_B$ = ______

(iv)

Open the switch.

(d)

Change $w$ and repeat (a)(ii), (b) and (c) until you have six sets of values of $w$ , $I_A$ and $I_B$ .

Include values of $\frac{(I_A + I_B)}{I_A I_B}$ in your table.

10M

(e)

(i)

Plot a graph of $\frac{(I_A + I_B)}{I_A I_B}$ on the $y$ -axis against $w$ 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 $I_A$ , $I_B$ and $w$ are related by the equation

\frac{(I_A + I_B)}{I_A I_B} = Mw + N

where $M$ and $N$ are constants.

Using your answers in (e)(iii), determine values for $M$ and $N$ . Give appropriate units.

$M$ = ______
$N$ = ______

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