The earth's surface has a negative surface charge density of `10^(-9) Cm^(-2)` . The potential difference of 400 kV between the top of the atmosphere and the surface results (due to low conductivity of the lower atmosphere) in a current of only 1800 A over the entire globe. If there were no mechanism of sustaining atmosphereic electric field , how much time (roughly) would be required to neutralise the earth's surface ? (This never happens in practice because there is a mechanism to replenish electric charges namely the continual thunder storms and lightning in different parts of the globe). Radius of the earth `= 6.37 xx 10^(6) m`.

Explanation

To find the time required to neutralize the Earth's surface charge, we will follow these steps:

### Step 1: Understand the given data
- Surface charge density, \( \sigma = 10^{-9} \, \text{C/m}^2 \)
- Current, \( I = 1800 \, \text{A} \)
- Radius of the Earth, \( r = 6.37 \times 10^6 \, \text{m} \)

### Step 2: Calculate the total surface area of the Earth
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