How long does it take a 750W heater to raise the temperature of 1kg of...
PHYSICS
JAMB 1991
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]
- A. 84s
- B. 112s
- C. 168s
- D. 280s
Correct Answer: C. 168s
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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