A student sets up a circuit to determine the resistance of a length of wire. The circuit contains a battery of unknown e.m.f., a length of a wire used to make a resistor X, an ammeter, a voltmeter and a variable resistor R. (a) Fig. 6.1 shows part of the circuit diagram. [Figure 6.1]

1. (a)(i)On Fig. 6.1, complete the circuit diagram by adding one voltmeter and one ammeter in suitable places to allow the determination of the resistance of X.[1]
2. (a)(ii)Explain how X and R act as a variable potential divider.[2]
3. (b)(i)The student determines the resistance of the resistor X for five different lengths of the wire making it. The lengths of wire range from 20cm to 60cm. The type of wire and the cross-sectional area of the wire are kept constant. Fig. 6.2 shows a graph of the results. [Figure 6.2] State the relationship between the resistance of the wire and the length of the wire.[1]
4. (b)(ii)Calculate the current in a 90cm length of the wire when there is a potential difference (p.d.) of 9.0 V across it. Show your working. current = .................................................... A[3]
5. (b)(iii)The p.d. across the wire making the resistor X is kept constant for all the measurements of resistance. Describe the relationship between the current in the wire and the length of the wire.[2]
6. (c)State how the resistance of a wire depends upon the cross-sectional area of the wire.[1]

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