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  • How to solve this problem- If voltage across a bulb rated 220 volt - 100 watt drops by 2.5% of its rated value, the percentage of the rated value by which the power would decrease is:

If voltage across a bulb rated 220 volt - 100 watt drops by 2.5% of its rated value, the percentage of the rated value by which the power would decrease is:

  • Option 1)

    20%

  • Option 2)

    2.5%

  • Option 3)

    5%

  • Option 4)

    10%

 

Answers (1)

P=\frac{V^{2}}{R}=\frac{\Delta P}{P}=\frac{2\Delta V}{V}+\frac{\Delta R}{R}\\ \frac{\Delta P}{P}=2\times 2.5+0=5\%


Option 1)

20%

This option is incorrect 

Option 2)

2.5%

This option is incorrect 

Option 3)

5%

This option is correct 

Option 4)

10%

This option is incorrect 

Posted by

Vakul

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