What is power? How do you differentiate ’ kilowatt from kilowatt hour? The Jog Falls in Karnataka state are nearly $20\ m$ high. $2000\ tonns$ of water falls from it in a minute. Calculate the equivalent power if all this energy can be p utilized? $(g=10\ ms^{-2})$

AcademicPhysicsNCERTClass 9

Power: The rate of work done or energy transfer with respect to time is said to be the power. It is denoted by $P$. 

Power $P=\frac{work\ done(W)}{time(t)}$

SI unit of power is Joule/second or Watt.


Kilowatt is the unit of power. In short, it is written $KW$.

$1\ Kilowatt=1000\ Watt$

While Kilowatt-hour is a commercial unit of energy.

$1\ Kilowatt-hour=3.6\times10^6\ Joule$

Mass of water $=2000\ tonns=2000\times10^3\ kg=2\times10^6\ kg$

Height $h=20\ m$

Therefore, the energy possessed by water at the given height,

$E=mgh$

$=2\times10^6\ kg\times 10\ ms^{-2}\times20\ m$

$=4\times10^8\ Joule$

Power generated $P=\frac{energy}{time}$

$=\frac{4\times10^8\ Joule}{60\ second}$

$=\frac{2}{3}\times 10^7\ W$

raja
Updated on 10-Oct-2022 13:28:52

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