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 -
C.
60.0(^o)C
Correct Answer: Option 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
There is an explanation video available below.