Suggest one material that could be used for the insulating stand.
On Fig. 11.1, draw how the charges are arranged on the sphere.
Explain what occurs to the charge on the sphere when a metal wire connected to earth is brought into contact with the sphere.
Describe what happens in the wire as the rod is taken away.
A circuit has a 7.5 V d.c. power supply and three resistors. Fig. 11.2 gives the circuit diagram. The diagram shows a d.c. power supply marked "+" and "-", an 18 Ω resistor in series with a parallel pair made up of a 60 Ω resistor and a 15 Ω resistor. Determine the total resistance of the circuit.
Calculate the current supplied by the power supply.
The current is not the same in the three resistors shown in Fig. 11.2. Underline the resistor in which the current is 1. the largest, 15 Ω resistor 18 Ω resistor 60 Ω resistor 2. the smallest. 15 Ω resistor 18 Ω resistor 60 Ω resistor
The 7.5 V d.c. power supply is formed from five 1.5 V cells. In the space below, draw a diagram to show the arrangement of the cells.
The 18 Ω resistor is made of metal. State and explain how the current in this resistor changes as its temperature increases.