Question

Assertion (A): Woolen clothes keep the body warm in winter.
Reason (R): Air is a bad conductor of heat.
A. Both A and R are true.
B. Both A and R are false.
C. Both A and R are true, R is the correct explanation of A.
D. Both A and R are true, R is not the correct explanation of A.

Answer 1

Hint: In winter if the heat loss from our body to the surroundings is prevented then we can feel warm. This is what a woolen cloth does. The woolen clothes have a large amount of air trapped in it

Complete step by step answer:
In winter we use woolen clothes to keep ourselves warm. Woolen clothes have the ability to prevent the loss of heat from our body into the surroundings.
This is because woolen clothes have a large amount of air molecules trapped inside. The presence of these large amounts of air molecules will make it an insulator to heat. We know that air is a bad conductor of heat. So, because of the air that is trapped in woolen clothes the heat from our body will not be conducted to the surroundings.
We know that heat flow happens from higher temperature to lower temperature. In winter since the outside temperature is low the heat from our body will flow towards the outside. If we prevent this flow of heat then we can feel warm. If we use woolen clothes the air trapped in it will prevent this flow of heat from our body and thus it will keep us warm.
Hence the assertion given is true and the reason that air is a bad conductor of heat is also true.
The given reason is the correct explanation of the assertion.
Hence, the correct answer is option C.

Note: Woolen clothes can prevent the flow of heat from our body with the help of air molecules trapped in it. But cotton clothes will not keep us warm in winter since they are so thin that they don't have much air trapped in between to act as an insulator.