Q: An electric kettle takes 4 A current at 220 V. how much time will it take to boil 1 kg of water from temperature 20 °C ? The temperature of boiling water is 100 °C .
(a) 12.6 min
(b) 4.2 min
(c) 6.3 min
(d) 8.4 min
Ans: (c)
Sol: E = V i t = ms ΔT
220 × 4 × t = 1 × 4200 (100 – 20)
t = 381. 85 = 6.3 min