An immersion heater rated 2.0A, 240V is used to boil water from temperature 52°c to 100°c. If the mass of the water is 2.5kg. determine the time taken to boil the water. [specific heat capacity of water = 4.2 x 103 jkg-1 k-1]
A. 1.05 x 103s B. 1.05 x 105s C. 1.05 x 102s D. 1.05 x 104s
Correct Answer: A
Explanation
Power of heater = lvt = 2 x 240 x t heat required to boil the water = Mct = 2.5 x 4.2 x 103 x (100.52) = 2.5 x 4. 2 x 103 x 48 2 x 240 x t = 2.5 x 4.2 x 103 x 48 ∴ t = (2.5 x 4.2 x 103 x 48)/2 x 240 = 1050s or 1.05 x 103s
