Fig. 11.1 shows a negatively charged rod close to an uncharged metal sphere that is mounted on an insulating stand. [Figure 11.1]

1. (a)(i)Suggest a material for the insulating stand.[1]
2. (a)(ii)On Fig. 11.1, draw the distribution of charges on the sphere.[2]
3. (a)(iii)1.A metal wire connected to earth is touched against the sphere. Explain what happens to the charge on the sphere.[3]
4. (a)(iii)2.The earth wire remains in contact with the sphere. Describe what happens in the wire as the rod is moved away.[1]
5. (b)(i)A circuit contains a 7.5V d.c. power supply and three resistors. Fig. 11.2 is the circuit diagram. [Figure 11.2] Determine the total resistance of the circuit. resistance = [3]
6. (b)(ii)Calculate the current in the power supply. current = [2]
7. (b)(iii)There is a different current in each of the three resistors in the circuit in Fig. 11.2. Underline the resistor in which the current is 1. the largest, 15Ω resistor 18Ω resistor 60Ω resistor 2. the smallest. 15 Ω resistor 18 Ω resistor 60Ω resistor[1]
8. (b)(iv)The 7.5 V d.c. power supply is made from five 1.5V cells. In the space below, draw a diagram that shows how the cells are arranged.[1]
9. (b)(v)The 18 Ω resistor is made of metal. State and explain what happens to the current in this resistor as its temperature increases.[1]

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