Question

Thermal diffusivity of the material depends upon -
(A). Thermal conductivity
(B). Mass density
(C). Specific heat
(D). Moisture content

Choose the correct answer from the options given below:

• A. (A), (B) and (C) only.
• B. (B), (C) and (D) only.
• C. (A), (B), (C) and (D).
• D. (C) and (D) only.

Hint:

For agricultural commodities, moisture content is the single most dominant factor influencing all physical, mechanical, and thermal properties.
Always include moisture content when analyzing biological materials.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Thermal diffusivity (\(\alpha\)) is a physical property that measures the rate at which heat propagates through a material relative to its ability to store thermal energy.

Step 2: Key Formula or Approach:
The mathematical definition of thermal diffusivity is:
\[ \alpha = \frac{k}{\rho \cdot c_p} \] where:
\(k\) = thermal conductivity
\(\rho\) = mass density
\(c_p\) = specific heat

Step 3: Detailed Explanation:
1. By definition, thermal diffusivity directly depends on thermal conductivity (A), mass density (B), and specific heat (C).
2. For agricultural and biological materials, all three core thermal parameters (\(k, \rho, c_p\)) are highly dependent on the

moisture content (D) of the material because water has exceptionally high specific heat and unique thermal properties compared to dry matter.
Consequently, the overall thermal diffusivity of any biological material depends significantly on its moisture content.
Therefore, thermal diffusivity depends upon all four factors: (A), (B), (C), and (D).

Step 4: Final Answer:
The correct option is 3, which corresponds to (A), (B), (C) and (D).