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How long does it take a 750W heater to raise the temperature of 1kg of water from 20oC ...

How long does it take a 750W heater to raise the temperature of 1kg of water from 20oC to 50oC [specific heat capacity of water = 4200Jkg-1K-1]
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  • A 84s
  • B 112s
  • C 168s
  • D 280s
Correct Answer: Option C
Explanation:
Heat energy = Elect. energy
mc\(\theta\) = power x time
1 x 4200 x (50 - 20) = 750 x t
t = 168s

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