Question

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

• A. $160\, MW$
• B. $80 \,MW$
• C. $20 \,MW$
• D. $500\, KW$

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
$P =\frac{W}{t}=\frac{8 \times 10^{6}}{0.1}=80 \times 10^{6} W$
$=80 \,MW$