Question

The surface charge density (in $C{m}^{-2}$ ) of the earth is about

• A. $10^{-9}$
• B. $-10^{-9}$
• C. $10^{-9}$
• D. $-10^{-9}$

Answer 1

Answer: (D)

Charge on the earth $=-0.5\times 10^{6}C$
Charge density $=\frac{\text{ charge }}{\text{ area }}$
Charge density $=\frac{0.5\times 10^6}{4\pi \times {\left(6400\times 10^3\right)}^2}$
$=-10^{-9}C{m}^{-2}$