Question

Which of the following is not an example of convectiton?

(a) After a car is turned on, the engine becomes hot.

(b) Steaming cup of hot tea

(c) Ice melting

(d) Hot air balloon

I have been asked this question in an interview for job.

I'd like to ask this question from Concentration Gradients and Reaction Rates in Solid Catalysts in portion Heterogenous Reactions of Bioprocess Engineering

Answer 1

The correct answer is:

(c) Ice melting

Ice melting is a phase change that occurs due to the heat being absorbed by the ice, but it is not an example of convection. Convection involves the transfer of heat through the movement of fluids (liquids or gases), where warmer fluid rises and cooler fluid sinks, transferring heat in the process.

Here's why the other options are examples of convection:

• (a) After a car is turned on, the engine becomes hot: This involves convection, as the hot fluids (coolant or air) in the engine circulate, transferring heat.
• (b) Steaming cup of hot tea: The steam rising from the hot tea is a form of convection as hot air moves upward.
• (d) Hot air balloon: The heated air inside the balloon rises, which is an example of convection.

Melting ice involves heat transfer through conduction (from a warmer object or air to the ice), not convection.