Verified Solution • 2025–26 Session moderate

QJEEM22Phb9f1: JEE Main 2022 Physics - Class 11 JEEM22Phb9f1 Solution: Water falls from a 40 m high dam at the rate of 9 10 4 kg per…

Water falls from a 40 m high dam at the rate of 9 ×\times 104 kg per hour. Fifty percentage of gravitational potential energy can be converted into electrical energy. Using this hydroelectric energy number of 100 W lamps, that can be lit, is :

(Take g = 10 ms −- 2)

Multiple Choice Options

  • A 25
  • B 50
  • C 100
  • D 18

Step-by-Step Verified Solution

Total gravitational PE of water per second =mghT= {{mgh} \over T}

=9×104×10×403600=104= {{9 \times {{10}^4} \times 10 \times 40} \over {3600}} = {10^4} J/sec

50% of this energy can be converted into electrical energy so total electrical energy =1042=5000= {{{{10}^4}} \over 2} = 5000 W

So total bulbs lit can be =5000 W100 W=50= {{5000\,W} \over {100\,W}} = 50 bulbs

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