JEE Mains Model Paper 13

The earth’s surface has a negative surface charge density of 10−9C∕m2. The potentialdifference of 400 kV between the top of the atmosphere and the surface results (due to the lowconductivity of the lower atmosphere) in a current of only 1800 A over the entire globe. Ifthere were no mechanism of sustaining atmospheric electric field, how much time (roughly)would be required to neutralize the earth’s surface ? (This never happens in practice becausethere is a mechanism to lightning in different parts of the globe. Radius of earth = 6.37 x 106m). In sec