$Assertion :$ When a glass of hot milk is placed in a room and allowed to cool,its entropy decreases.
$Reason :$ Allowing a hot object to cool does not violate the second law of thermodynamics.

$A$ solid body of constant heat capacity $1 \ J/^oC$ is being heated by keeping it in contact with reservoirs in two ways :
$(i)$ Sequentially keeping in contact with $2$ reservoirs such that each reservoir supplies same amount of heat.
$(ii)$ Sequentially keeping in contact with $8$ reservoirs such that each reservoir supplies same amount of heat.
In both the cases,the body is brought from initial temperature $100^oC$ to final temperature $200^oC$. The entropy change of the body in the two cases respectively is :

Which of the following statements is correct for any thermodynamic system?

Why is a heat engine never $100\%$ efficient?

Can the whole of heat be converted into work?

$100^{\circ} C$ temperature wala ek garam tambe ka tukda $30^{\circ} C$ temperature wale talab mein dala jata hai. Tamba thanda hokar $30^{\circ} C$ par aa jata hai,jabki talab bahut bada hone ke karan apne prarambhik taapman par bana rehta hai. Tab,