An immersion heater is rated 836 watt. It should heat 1 litre of water from 10^{0}C to 40^{0}C in about

  • Option 1)

    200 sec

  • Option 2)

    150 sec

  • Option 3)

    100 sec

  • Option 4)

    120 sec

 

Answers (1)

As we learnt in 

Power dissipated in external resistance -

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

-

 

 

Amount of energy required = m s \Delta T

                                           = 1 kg \times (4.18 J/g) \times 30

                                          = 4180 \times 30J= 125400J

Time required = \frac {E}{P}= \frac{125400}{836}= 150 sec

                      =2.5\ minutes


Option 1)

200 sec

Incorrect

Option 2)

150 sec

Correct

Option 3)

100 sec

Incorrect

Option 4)

120 sec

Incorrect

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