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# An electric heating coil rated at 1KW is used to heat 2kg of water for 2 minutes...

### Question

An electric heating coil rated at 1KW is used to heat 2kg of water for 2 minutes. The initial water temperature is 30$$^o$$C. Taking the specific heat of the water as 4,000Jkg $$^{-1}$$ and neglecting that of the container, the final water temperature is

### Options

A)
15.0$$^o$$C
B)
45.0$$^o$$C
C)
52.5$$^o$$C
D)
25.0$$^o$$C

### Explanation:

Power = 1kw = 100W
Time = 2mins = 2 × 60 = 120secs
Energy = power × time
1000 × 120 = 120,000J
Energy = mc(θ$$_2$$ – θ$$_1$$)
120,000 = 2 × 4000(θ$$_2$$ – θ$$_1$$)
θ2 = 30 + 15 = 45 $$^o$$ C

## Discussion (2)

• I keep failing what I got
The question is is solved correctly but answer is wrong the answer nis
45°C B

• Power = 1kw = 100W
Time = 2mins = 2 × 60 = 120secs
Energy = power × time
1000 × 120 = 120,000J
Energy = mc(θ$$_2$$ – θ$$_1$$)
120,000 = 2 × 4000(θ$$_2$$ – θ$$_1$$)
θ2 = 30 + 15 = 45 $$^o$$ C