Question

A circular metal loop is heated at point $O$ as shown in above Figure.
(i) In which direction would heat flow in the loop?
(ii) In which order the pins at points $P$ , $Q$ and $R$ are fixed with the help of wax fall if points $O$ , $P$ , $Q$ and $R$ are equidistant from each other?

Answer 1

Hint: This question utilizes the concept of Heat Transfer. We know that in a conductor like metal, heat travels through conduction. Conduction takes place when two bodies are in physical contact with each other. Here, the metal loop is totally solid, so conduction takes place in the metal loop.

Complete step by step answer:

According to the given figure, the heat from the candle is transferred to the loop at point $O$ through convection. Once the heat reaches $O$, it is transferred throughout the metal loop through conduction.

(i) The heat flows from hotter to colder regions. Thus, the heat will start flowing from point $O$ towards point $Q$.

(ii) It is given that the points $O$ , $P$ , $Q$ and $R$ are equidistant from each other. We know that the heat will flow from point $O$ towards point $Q$. Since, the metal loop is uniform in nature and the distance $OP$ and $OR$ are the same, we could infer that- after heating the metal loop at point $O$ , the pins attached at point $P$ and point $R$ will fall down simultaneously. Then, after some more time, the pin at point $Q$ will fall off.

Note: Convection is the transfer of heat through fluid medium (through air here) and conduction is the transfer of heat through a solid medium. Here, the heat from the candle to the loop is transferred through convection. Then, the transfer of heat from one point of the metal loop to another is through conduction.