1.1. A student is determining the resistance of a resistance wire.

The circuit is shown in Fig. 2.1.

Record, in amperes A, the current $I$ in the circuit, as shown on the ammeter in Fig. 2.2.

$I$ = ........................................................ 

1.2. The student places the sliding contact C at a distance $l$ = 20.0 cm from B.

  She records the potential difference V across the length $l$ of the resistance wire.

  She repeats the procedure using $l$ values of 40.0 cm, 60.0 cm, 80.0 cm and 100.0 cm. All the readings are shown in Table 2.1.

Calculate, and record in Table 2.1, $\frac{V}{l}$ for each value of $l$.

Complete the $\frac{V}{l}$ column heading.

Table 2.1

1.3. Look carefully at the values in Table 2.1.

(i) Tick the box to show your conclusion from the results.

$□$ $\frac{V}{l}$ is approximately constant.

$□$ $\frac{V}{l}$ is decreasing as V increases.

$□$ $\frac{V}{l}$ is increasing as V increases.

$□$ There is no simple pattern for $\frac{V}{l}$in the results.

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(ii) Justify your conclusion by reference to your results.

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1.4. Calculate the resistance of 100 cm of the resistance wire.

Use the equation $R=\frac{V}{I}$where V is the potential difference across 100 cm of the resistance wire. Use the value of current $I$ from part (a). Give your answer to a suitable number of significant figures for this experiment and include the unit.

R = ........................................................ 

1.5. In this type of experiment, it is sensible to keep the temperature of the resistance wire as close to room temperature as possible. Suggest one way to minimise the rise in temperature of the resistance wire.

1.6. Draw the circuit symbol for a variable resistor.