Question

In a variable state, the rate of flow of heat is controlled by
A. Density of material
B. specific heat
C. Thermal conductivity
D. All the above factors

Answer 1

Hint:In order to solve this problem we need to understand the rate of heat transfer. The rate of flow of heat is the amount of heat that is transferred per unit of time. Here, using the formula for heat flow we are going to find the solution.

Formula Used:
To find the rate of flow of heat the formula is,
\[\dfrac{Q}{t} = KA\dfrac{{\Delta T}}{L}\]
Where, A is a cross-sectional area, \[\Delta T\] is the temperature difference between two ends and L is the length of the cylinder.

Complete step by step solution:
We know that to find the rate of flow of heat the formula is,
\[\dfrac{Q}{t} = KA\dfrac{{\Delta T}}{L}\]
Which can be written as,
\[\dfrac{Q}{t} \propto K\]
The above equation says that the rate of flow of heat depends on the thermal conductivity that is the rate of flow of heat is controlled by K. (Inversely proportional to K)

And \[\dfrac{Q}{t} \propto \dfrac{1}{{\rho c}}\]
Here, \[\rho \] is the density and c is specific heat. This means the rate of flow of heat depends also on the density and specific heat. Therefore, the rate of flow of heat is controlled by all the above factors.

Hence, option D is the correct answer.

Note:Here in the given problem do not get confused with the formula for thermal conductivity and the rate of heat transfer. Since thermal conductivity and heat transfer are related to each other. And need to remember what factors the rate of flow of heat depends on.