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Current Electricity question

2008 · Q125
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Current Electricity question

2008 · Q125

NEETPhysicsCurrent ElectricityMCQ+4 / −1
An electric kettle takes 4 A current at 220 V. How much time will it take to boil 1 kg of water from temperature 20oC ? The temperature of boiling water is 100oC
  1. A
    12.6 min
  2. B
    4.2 min
  3. C
    6.3 min
  4. D
    8.4 min
View written solutionFree

Correct answer: C

Power = 220 V × 4 A = 880 watts. = 880 J/s.
Heat needed to raise the temperature of 1 kg water through 80°C

= ms.Δ\Delta ΔT × 4.2 J/cal

= 1000 g × 1 cal/g × 80 × 4.2 J/cal.

∴\therefore∴ Time taken = 1000×1×80×4.2880=336×103880{{1000 \times 1 \times 80 \times 4.2} \over {880}} = {{336 \times {{10}^3}} \over {880}}8801000×1×80×4.2​=880336×103​

= 382 s = 6.3 min.

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