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Question
What is power? How do you differentiate kilowatt from kilowatt-hour? The Jog Falls in Karnataka state are nearly 20 m high. 2000 tonnes of waterfalls from it in a minute. Calculate the equivalent power if all this energy can be utilized? (g = 10 m s–2)
Solution
Power is defined as the rate of doing work or the rate of transfer of energy, Kilowatt is the unit of power and kilowatt-hour is the unit of energy or work as a kilowatt-hour
= unit of power × unit of time.
Energy possessed by 2000 tonnes
(= 2000 x 103 kg) water at a height of 20 m, Ef, = mgh
= 2000 x 103 x 10 x 20
= 4 x 108 J
Power generated if all this energy can be
utilized,
P = `"E"_"p"/"t"`
= `(4 xx 10^8 "J")/(60"s")` (∵ t = 1 min = 60 s)
= `2/3 xx 10^7 "W"`
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