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Staedy Conduction Heat Transfer MCQ - Practice Questions with Answers

Edited By admin | Updated on Sep 25, 2023 25:23 PM | #NEET

Quick Facts

Basics of conduction is considered one of the most asked concept.
14 Questions around this concept.

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The figure shows a system of two concentric spheres of radii $r_1$ and $r_2$ and kept at temperatures $T_1$ and $T_2$ respectively. The radial rate of flow of heat in a substance between the two concentric spheres is proportional to

$\frac{r_1 r_2}{\left(r_2-r_1\right)}$

$\ln \left(r_2-r_1\right)$

$\frac{\left(r_2-r_1\right)}{r_1 r_2}$

$\ln \left(\frac{r_2}{r_1}\right)$

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Concepts Covered - 1

Basics of conduction

In the previous concept, we have learned the defination of Conduction. Now we will discuss the characterstics and properties of conduction -

(1) Heat flows from high temperature to low temperature. In this the particles of the medium simply vibrate about its mean position but do not leave their place.
(2) Conduction heat transfer is medium dependent.
(3) The temperature of the medium goes on increasing in the direction of heat transfer.
(4) Conduction mode of heat transfer is the process which is possible in all states of matter.
(5) In solids, the only mode of heat transfer is conduction.

(6) In metallic solids, free electrons carry is the heat energy carrier, therefore they are good conductor of heat.

Terminologies used in steady state or basics of conduction -

Steady state : It means that the temperature in the system is not time dependent. So, if we supply heat to a body then the temperature of the body increases but after sometime, a state is reached when the temperature of every cross-section of the rod becomes constant. In this state, no heat is absorbed by the rod. This state of the rod is called steady state.

Isothermal surface : Any cross-section (within a conductor) having its all points at the same temperature, is called isothermal surface.

Temperature gradient : The rate of change of temperature with distance between two isothermal surfaces is called temperature gradient. It is denoted by -
So,

$\begin{array}{l}{\text {Temperature gradient }=\frac{- \Delta \theta}{\ \ \Delta x}} \\ {\text {The negative sign show that temperature } \theta \text { decreases as the }} {\text {distance } x \text { increases in the direction of heat flow. }}\end{array}$

Thermal conductivity(K) - It is the measure of the ability of a substance to conduct heat through it. The magnitude of K depends only on nature of the material. Substances which do not permit easy flow of heat are called bad conductors. They possess low thermal conductivity due to very few free
electrons.