Question

Liquid is filled in a vessel which is kept in a room with temperature ${20}^{\circ }C$. When the temperature of the liquid is ${80}^{\circ }C$, then it losses heat at the rate of 60 cal/sec.What will be the rate of loss of heat when the temperature of the liquid is ${40}^{\circ }C$.

• A. 180 cal/sec
• B. 40 cal/sec
• C. 30 cal/sec
• D. 20 cal/sec

Answer 1

The correct option is D 20 cal/sec

We know rate of heat transfer

$q=hA\Delta T$

or

$q=C\Delta T$

where C is constant

$60=C.(80-20)$

$60=C\times 60$

$c=1$

for $q={40}^{\circ }$

$q=c(40-20)$

$=1\times 20$

$q=20cal/sec$