An
aluminium electric kettle of mass 0.560 kg
contains a 2.40-kW
heating element. It is filled with
0.640 L of water at
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Solution: Click For PDF Version (a)
Mass of 0.640
L of water
Amount of
heat required for heating the water from
In
calculating the amount of heat required we have used for the thermal
capacity of water
Mass of the
aluminium kettle is 0.560 kg and the specific heat of aluminium is
Total heat
required for the water to boil in the kettle will be
Rate at which
heat energy is supplied by the heating element is
Therefore, the time required for the kettle to boil will be
(b)
Heat of
vaporization of water
Therefore,
amount of heat required for 0.640 kg of water to vaporize at
Therefore,
the additional time taken for vaporization of water at
And the total
amount of time taken for vaporization of 0.640 L of water at
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.
We have to calculate
(a) the time taken for the water to boil;
(b) the time for the kettle to boil dry.
(We may assume that the temperature of the
kettle does not exceed
at any time.)
Heat required for the kettle to get warmed from
