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