In ancient times when lightning was the privilege of 'devine beings', a question - 'how much does lightning cost ?' would have been regarded as a sin. Today, electricity is a commodity that can be measured and priced like any other. The potential of a lightning discharge is `25` million volts and the maximum intensity of the current rating is `200,000` amperes.
(a) What is the power of the discharge ?
(b) What is the energy spent in the lightning if it lasts for `0.001 s` ?
( c) What is the approximate cost of a lightning discharge ?
(d) What message did nature convey to the man through lightning ?

Explanation

(a) `P = VI = (25 xx 10^6 V)/(2 xx 10^5 A) = 5 xx 10^12 W`
`5000 xx 10^6` kW = 5000 million kilowatts
(b) Energy spent in the lightning `= Pt = (5 xx 10^9 kW)(2.8 xx 10^-7 h) = 1400 kWh`
`("as" t = 0.001 s = (0.001)/(3600) h = 2.8 xx 10^-7 h)`
(c) Cost of a lightning discharge `= (1400 kWh)(7//kWh) ~~ 10,000`
This is no cost for such a grand natural spectacle
(d) Lightning prompted man to generate electricity on Earth. Thus, nature is always there to teach us - only we have to keep our eye and minds open to be receptive.