A 210 W heater is used to heat 100 g water. The time required to raise the temperature of this water from `25^(@)C` to `100^(@)C` is (specific heat capacity of water `=4200" J/Kg-"^(@)C`)

Options

A. 100 s
B. 125 s
C. 150 s
D. 200 s

Answer

C

Explanation

Given, specific heat of water,
`W=4200" J/kg"^(@)C=4.2xx10^(3)" J/kg"^(@)C`
mass of water, `m=100 g=10^(-1)` kg
and power of heater, `H=Q/t=210 W`
`implies Q=210 t` ...(i)
where Q is amount of heat required to raise the temperature of water which is given by
`Q=m c Delta T`
`210t=m c Delta T` [From Eqs. (i)]
`210 t=10^(-1) xx4.2xx10^(3)xx75`
`t=(10^(-1)xx4.2xx10^(3)xx75)/210=150 s`
Therefore, the time required to raise the temperature of water is 150 s.