An electric kettle takes 4A current at 220V. How much time will it take to boil 1 kg of water from room temperature 200 C? (the temperature of boiling water is 1000C) (a) 12.6 min (b) 12.8 min (c) 6.3 min (d) 6.4 min

Given

m = 1 kg = 1000 g

specific heat capacity of water, s = 1 cal/g.0 C

Heat required, Q = ms (ΔT)

= 1000 x 1 x (100 – 20)

We get,

Q = 1000 – 80cal ——- (1)

Heat produced in time t is given by,

H = VIt

H = 220 x 4 x t Joule

H = (220 x 4 x t)/4.18 Cal —— (2)

Now, equating equation (1) and (2)

Hence,

(220 x 4 x t)/4.18 = 1000 x 80

t = (1000 x 80 x 4.18)/220 x 4

We get,

t = 380 s

t = 6.3 min

Hence, the correct option is (c).

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