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  • Water falls from a 40 m high dam at the rate of  kg per hour. Fifty pe

Water falls from a 40 m high dam at the rate of \mathrm{\text 9 \times 10^{4}} kg per hour. Fifty percentage of gravitational potential energy can be converted into electrical energy. Using this hydro electric energy number of 100 W lamps, that can be lit, is :

\mathrm{\left(\text { Take } \mathrm{g}=10 \mathrm{~ms}^{-2}\right)} 

Option: 1

25


Option: 2

50


Option: 3

100


Option: 4

18


Answers (1)

\mathrm{\frac{P E}{\text { time }} =\frac{9 \times 10^{4} \times 40}{60 \times 60}} \\


              \mathrm{=\frac{36\times 10^{6}}{3600}=10^{4}\frac{J}{s}}

Electrical energy per sec

                   \begin{aligned} &=50 \% \times 10^{4} \\ &=\frac{10^{4}}{2} \mathrm{~J} / \mathrm{s}=\frac{10^{4} \mathrm{}}{2}W \end{aligned}

Let N no.of bulbs lit

\mathrm{N\times 100}=\frac{10^{4}}{2}

\mathrm{N=\frac{100}{2}=50}

Hence correct answer is 2

Posted by

Kshitij

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