Question

Find the time taken by a $500W$ heater to raise the temperature of $50kg$ of material of specific heat capacity $900Jk{g}^{-1}{K}^{-1}$ from ${18}^{\circ }C$ to ${38}^{\circ }C$. Assume that all the heat energy supplied by heater is given to the material.

• A. $16min$
• B. $64min$
• C. $30min$
• D. $30sec$

Answer 1

The correct option is C $30min$

Heat energy $E=ms(T_2-T_1)$

Heat required is $E=900\times 50\times (38-18)=900\times {10}^{3}J$

So the time required by heater of power $500W$ to supply this amount of heat is

$△t=\frac{E}{P}=\frac{900\times {10}^3}{500}=1800sec=30min$