An electric heater rated 220V; 1000W is immersed into a bucket full of water; calculate the mass of water if the temperature changes from 30°C to 100°C and the current flows for 300seconds. [specific heat capacity of water = 4200 jkg‾¹K‾¹]

A. 4.28 kg
B. 42.86 kg
C. 1.02 kg
D. 7.14 kg

Correct Answer:

Option C = 1.02 kg

Explanation

Energy supplied bythe heater = heater gained by water
pt = MCAθ
1000 x 300 = m x 4200(100 – 30)
m = (1000 x 300)/4200 x 70 = 1.02 kg