Question

Heat flows from
A. Higher temperature to lower temperature
B. Lower temperature to higher temperature
C. One body to other having same temperature
D. Body with higher heat content to one with lower heat content

Answer 1

The given case can be considered analogous to the flow current in a circuit. We could find the answer along with valid justification with the help of the second law of thermodynamics. This law states that nature tends to be in a state with high entropy. Find out for which of the given options the entropy is high and hence find the answer.

Complete Step by step solution:
In the question, we are asked to find from where to where the flow of heat takes place. In order to understand this, let us recall the second law of thermodynamics which states that it is the natural tendency for an isolated system to get degenerated into a more disordered one, that is, a system with greater entropy is known to be more stable.
We know that change in entropy is given by,
$\Delta S=\dfrac{\Delta Q}{\Delta T}$
Clearly, entropy will increase when heat is transferred from higher temperature to lower temperature. Also, we know that the entropy never decreases but increases for the case of any real processes.
The given case is similar to the flow of current from higher potential to lower potential. So we could say that the heat transfer occurs from higher temperature to lower temperature and this statement is justified by the second law of thermodynamics.

Hence, option A is the correct answer.

Note:
Entropy is defined as the degree of disorder. However, for a reversible process, the entropy remains constant but there is no known process that is reversible in real life. Also, for any irreversible process the entropy increases. And the universe has this natural tendency to be selective to systems with high entropy.