Question

The voltage of clouds is $4\times 10^{6}V$ with respect to ground. In a lightning strike lasting $\text{100 ms}$ , a charge of $\text{4 C}$ is delivered to the ground. The average power of lightning strike is (assume complete discharges )

• A. $\text{160 MW}$
• B. $\text{80 MW}$
• C. $\text{20 MW}$
• D. $\text{500 KW}$

Answer 1

Answer: (B)

Energy stored between cloud and earth, assuming the capacitor model is
$W=\frac{qV}{2}$
$\frac{4\times 10^6\times 4}{2}=8\times 10^{6}J$
The power of lightning strike is
$P=\frac{W}{t}=\frac{8\times 10^6}{0.1}=80\times 10^{6}W$
$=80MW$