You may not need to use all of the materials provided. In this experiment, you will investigate the variation of current in a circuit for different contact positions on a wire loop. (i) Assemble the circuit of Fig. 1.1. (ii) With lead X pressed on to the crocodile clip as shown in Fig. 1.1, adjust the rheostat until the ammeter reading is in the range $160\text{--}190\ \text{mA}$. (iii) Record the ammeter reading $I_0$ when the lead X is pressed on to the crocodile clip.…

Physics 9702/34 — 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

You may not need to use all of the materials provided.

In this experiment, you will investigate the variation of current in a circuit for different contact positions on a wire loop.

(a)

(i)

Assemble the circuit of Fig. 1.1.

Fig. 1.1

(ii)

With lead X pressed on to the crocodile clip as shown in Fig. 1.1, adjust the rheostat until the ammeter reading is in the range $160\text{--}190\ \text{mA}$ .

(iii)

Record the ammeter reading $I_0$ when the lead X is pressed on to the crocodile clip.

$I_0$ = ______

(b)

Move lead X and press it on to the wire approximately half way between A and B. Record its distance $l$ from A and record the ammeter reading $I$ .

$l$ = ______
$I$ = ______

(c)

Repeat (b) with the lead X at different distances from A until you have six sets of values of $l$ and $I$ .
Include values of $\frac{1}{I}$ and $l^2$ in your table.

10M

(d)

(i)

Plot a graph of $\frac{1}{I}$ on the $y$ -axis against $l^2$ 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 $l$ are related by the equation

\frac{1}{I} = al^2 + b

where $a$ and $b$ are constants.

Using your answers from (d)(iii), determine the values of $a$ and $b$ .
Give appropriate units.

$a$ = ______
$b$ = ______

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