You are provided with a knife edge, metre rule, two strings of 20 cm, each 50 g and 100 g masses. Perform experiment following procedures (a) to (e). (a) Balance a metre rule on a knife edge, mark the balancing point, write letter G at the balancing point using a pencil. (b) Use a Vernier calliper to determine the thickness, t and the width, w of the metre rule. (c) Place the metre rule on a knife edge so that the knife edge is at 65 cm mark. Suspend the given 100 g mass at a point which balances the metre rule. Record the distance between the knife edge and G as a cm, and between the knife edge and the position of 100 g mass as y. (d) Suspend the mass of 50 g on the left hand side of the knife edge at the position 45 cm and the adjust the position of 100 g mass to balance the metre rule as shown in Figure 21. Record the new value of y and then record the distance between the 50 g mass and the knife edge as x. (e) Repeat the procedures in 1 (d) by changing the position of 50 g to 40 cm, 35 cm, 30 cm and 25 cm. Answer the following questions:

1. Tabulate the results of x (in cm) and y (in cm). (4 mk)
2. Plot a graph of y against x. (5 mk)
3. Determine the slope of the graph. (3 mk)
4. Calculate the value of z from your experimental results given that, za y  Sx . 100 (6 mk)
5. State the physical significance of z. (3 mk)
6. State the aim of doing this experiment. (4 mk)

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Determine the resistivity of the material of the wire provided from the following procedures: (a) Use the micrometre screw gauge to determine the diameter of the given wire and hence find its cross section area in m2 . Connect the circuit as shown in Figure 26 where C is a crocodile clip. Measure the length of wire L = 100 cm and clip it so that the current flows across the wire. Record the voltmeter reading V. (b) Repeat the procedures in 2 (a) with crocodile clip at L 80 cm, 60 cm, 40 cm and 20 cm . Record the corresponding voltmeter reading in each case. 1 1 (i) Tabulate the values of L, V, and . (The length L should be in metres). L V 1   1   (ii) Plot a graph of V1 against L1 V L (iii) Determine the slope S. 1 (iv) Find the value of V for which  0 and state its physical meaning. L 1 A 1 1 (v) Determine the value of resistivity of the wire given that,   . V E L E

1. Tabulate the values of L, V, and 1/L, 1/V. (The length L should be in metres). (5 mk)
2. Plot a graph of 1/V against 1/L. (5 mk)
3. Determine the slope S. (3 mk)
4. Find the value of V for which 1/L = 0 and state its physical meaning. (4 mk)
5. Determine the value of resistivity of the wire given that, 1/V = A/(ρE) + 1/(EL). (8 mk)

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