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
A
15.0\(^o\)C
B
45.0\(^o\)C
C
52.5\(^o\)C
D
60.0\(^o\)C
Verified Correct Answer: B.
Physical Principles & Numerical Solution
Power = 1kw=100W
Time = 2mins = 2 \times 60 = 120secs
Energy = power \times time
1000 \times 120 = 120,000J
Energy = mc(\theta\(_2\) – \theta\(_1\))
120,000 = 2 \times 4000(\theta\(_2\) – \theta\(_1\))
\theta2 = 30 + 15 = 45 \(^o\) C
Source: Myschool Past Questions Archive (Record #47717)