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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

The correct answer is B.

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


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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

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