Leading up to a thunderstorm, a cloud layer 800 m above the Earth's surface acquires a negative electric charge. The cloud layer has an area of 10 m2. The air between the cloud and the ground has a relative permittivity of 1.0005. (a) Explain why electrons on the Earth's surface would move away from the region beneath the cloud. (0.5 mark) (b) Modelling the cloud layer and the ground beneath it as a parallel-plate capacitor, calculate the capacitance of this situation. (1 mark) (c) A potential difference of 108 V develops between the cloud and the ground. How much charge would be on the cloud layer? (1 mark) (d) How much energy is stored in this capacitor arrangement? (1 mark) (e) During a lightning strike, 1% of the stored charge flows between the cloud and Earth in one millisecond. What current does this correspond to? (1.5 marks)