# An electric kettle takes 4 A current at 220 V. How much time will it take to boil 1 kg of water from room temperature $20^{0}C$? The temperature of boiling water is $100^{0}C$ Option 1) 6.4 minutes Option 2) 6.3 minute Option 3) 12.6 minutes Option 4) 12.8 minutes

As we learnt in

Power dissipated in external resistance -

$P=(\frac{E}{R+r})^{2}R$

-

Total energy required = m s $\Delta$T

= 1000 $\times$ 1 cal/g $\times$ 80

= 80000 $\times$ 4.2 J = 336000J

$\therefore time \ required = \frac{energy}{power}= \frac{33600}{VI}$

$=\frac{33600}{220\times4}=6.3\ min$

Option 1)

6.4 minutes

Incorrect

Option 2)

6.3 minute

correct

Option 3)

12.6 minutes

Incorrect

Option 4)

12.8 minutes

Incorrect

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