Question

Assertion
Warming a room by a heat blower is an example of forced convection.
Reason
Natural convection takes place due to gravity
1) Both Assertion and the Reason are correct and reason is the correct explanation for Assertion.
2) Both Assertion and the Reason are correct but reason is not the correct explanation for Assertion
3) Assertion is correct but reason is incorrect
4) Assertion is incorrect but reason is correct

Answer 1

Hint:There are basically three types of heat transfer that takes place: conduction, convection and radiation. In conduction heat transfer takes place through solids, convection heat transfer takes place through fluid and in radiation heat transfer takes place without any medium.
Complete answer: Here the assertion is given that “Warming a room by a heat blower is an example of forced convection”, forced convection is a unique type of convection in which heat transfer takes place by forcing a fluid of higher or lower temperature to spreads around a particular place or area. The best example of this type of heat transfer is fan, in the case of fan the wind is forced by the rotation of the fan blades to spread out and cool the area , in a similar fashion heat blower works, the heat is first transferred to the air and then the air is forced to spread out in the area making that area warm. The given assertion is true. In nature, the heat of the Sun warms the water in the sea and the water evaporates as it becomes hot gas which is less dense and light in the meantime the colder air that is denser takes place that was left by the hot air. The hot air reaches certain heights and becomes dense and condenses and after a certain time it comes down as rain. In this whole process gravity plays a major role, as due to gravity the cold air and rain comes down. So, the given reason is true but it is not the correct explanation of the assertion as in the case of heat blower gravity doesn’t help in blowing the air nor heating the air.

Option “2” is correct. Both Assertion and the Reason are correct but reason is not the correct explanation for Assertion.

Note: Here, first explain about the forced convection and then explain the relation of forced convection with the assertion also give an example of natural convection and explain the role of gravity in natural convection, also provide the justification of choosing the particular option.