ICSE Class 10 Physics 2014 Solved Paper

Question : 55 of 66

Marks: +1, -0

Heat energy is supplied at a constant rate to

100 {\g}

of ice at

0^{∘} {\C}

. The ice is converted into water at

0^{∘} {\C}

in 2 minutes. How much time will be required to raise the temperature of water from

0^{∘} {\C}

20^{∘} {\C}

? [Given : sp. heat capacity of water

=4.2 {\J} {\g}^{-1}{ }^{∘} {\C}^{-1}

, sp. latent heat of ice

=336 {\J} {\g}^{-1}]

Solution:

Given :

m=100 {\g}, t=2

minutes

=2 × 60

sec.
Heat energy taken by ice at

0^{∘} {\C}

to convert to water at

0^{∘} {\C}

\; {\Q}=m {\L}=100 × 336=33600 {\J}

\; ∴ \;\; {\P}=\;{ {\Q}}/{t}=\;{33600}/{2 × 60}=280 {\J} \/ {\ s}

The heat energy required to convert water at

0^{∘} {\C}

20^{∘} {\C}

{\Q}\;=m c ∆ t=100 × 4.2 × 20=8400 {\J}

{\Q}\;= {\P} × t

8400\;=280 × t

t\;=30 {\ sec}=0.5 {\min} .

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