conduction only
convection only
radiation only
conduction and convection
convection and evaporation
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Although, the examiner might have CONVECTION in mind as the answer because he said open air (fluid), a closer look at the scenario reveals that all the three modes of heat transfer are called into play.
1. CONDUCTION is involved because heat is conducted from the centre of the ball through the molecules to the outer part which is colder.
2. CONVECTION is involved because the heated conducted out of the ball is transferred through the medium of air by convection current.
3. RADIATION is involved because any hot object radiates heat ( called radiant heat or infrared radiation).
Why some of you are confused about this radiation is due to the fact that we say that radiation does not require a material medium to take place. Get it right, it doesn't mean that heat does not radiate through a medium. It simply says that it doesn't require it before it will take place, i.e. whether a material medium or not, it will take place. For example, heat from the sun reaches us by radiation and there is a medium of air around the earth through which it passes, although if there were no air, it would have still reached us. And when you warm yourself near fire or near any hot object, it is by radiation although there is a medium of air between you and the object.
In summary, this question is ambiguous and the answer is not in the options. In order to avoid this ambiguity, the examiner should have put the question this way:
The ball loses heat mainly by....
In this case the answer will be CONVECTION because greater amount of heat is lost by convection.
This problem requires the authorities in physics like Prof P N. Okeke and indeed other of sch authority in physics to get it settled once and for all. Because lets look at it again, the suspended hot ball is in contact with the surrounding air ,(a material medium) hence those that are going out for radiation might well rethink. The hot object is a solid with its own molecules of the solid.It first conducts the heat between its solid molecule before beginning to heat up the surrounding air.Hotter molecules gives out its heat to colder oner ones before the heat reahes the surrounding air.Therefore to me Conduction is the first way the solid ball cools.Again once the heat reaches the surrounding air the closest air molecules gain the heat and transfer same to the immediate cold molecules and a convectional current soon sets up.Therefote another way is convection, hence the answer is Conduction and convection only.
It should be radiation cos it is suspended in air nd havin no contact to any oda material it definitely lost its heat to the surrounding through radiation
Summary for heat transfer:
Solid to solid = Conduction
Solid to liquid or gas= convection
No material medium = radiation
Air is material medium which consists of oxygen, carbon dioxide, rare gases, Nitrogen and water vapour.
B is legit ✓✓✓
calm down guys
it loses heat by convection mainly coz the cool air surrounds the ball and carry the heat away.
and by radiation too,the ball also emit heat as infrared radiation
but since you are given either convection or radiation and you have to pick one,I suggest you pick convection but if it's the two together in an option, you can pick them
The right ans is convection.This is because d heat transfer there occurs with air movement.The metal didn't come in contact with any material so it's nt conduction.There are air molecules around d metal (i.e no vaccuum),so it's nt radiation.It's definitely CONVECTION!
I really cannot agree with your answer
because radiation is what is involved when heat energy is transferred through air as the primary medium so why convection
The correct answer is Convection because convection is heat transfer method in fluids, conduction is heat transfer method in solids and in radiation no material medium is required.
Thanks for your contributions. Correction has been made, the correct answer is B.
