1.
5. An electric kettle market 1 kW, 230V, takes 7.5 minutes
to bring 1 kg of water at 15°C to boiling point. Find the
efficiency of the kettle.
(Ans : 79.07%)
Answers
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1
The efficiency of the kettle is 79 %.
Explanation:
We are given that:
- Power of electric kettle = 1 kW
- The voltage of electric kettle = 230 V
- Time taken by kettle to raise the boiling point of water = 7.5 minutes
- Mass of water = 1 Kg
- To Find: The efficiency of electric kettle = ?
Solution:
Heat produced = V x I x t = Pt
Heat produced = 1000 W x 7.5 x 60
Heat absorbed = 1 x 4200 (100 - 15) = 4200 x 85
Efficiency = Heat absorbed / heat produced x 100
= 4.2 x 85 x 10^3 / 4.5 x 10^5 x 100
= 357 / 4.5 = 79 %
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