Figure 6 shows two charged water droplets A and B in a thundercloud. The radius of A is 66 um and the radius of B is 35 um. Each droplet has a charge of -1.2 × 10-¹2 C. Assume that the charge on A and the charge on B are concentrated at their centres. The distance between the centres of A and B is 1.5 mm.

1 Calculate the electrostatic force between A and B. Movement of the air in the cloud causes A and B to move together until they touch. Calculate the work done against the electrostatic force in moving A and B from the position shown in Figure 6 to the position where they touch.

State the direction of Ey. A charged water droplet is stationary at Y. The weight of the droplet and the force on it due to Ey are equal in magnitude. The mass of the droplet is 1.38 × 10⁹ kg.X The charge on the droplet is -2.1 x 10-12 C. The base of the thundercloud and the ground beneath it can be modelled as two plates of a parallel-plate capacitor with air between them as shown in Figure 8. \text { Figure } 8 The base of the cloud is circular, with a diameter of 2.75 km.TI The base of the cloud is 340 m above the ground. Show that the capacitance of the capacitor is about 1.5 × 10-7 F. The capacitor discharges when lightning strikes the ground.The charge stored in the capacitor before it discharges is 87 C. Calculate the energy available for the lightning strikes.