Question

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).

Assertion (A): Thermal conductivity of a single grain is always greater than that of bulk grain.

Reason (R): Thermal conductivity of air is comparatively less than that of food grain.

In light of the above statements, choose the correct answer from the options given below.

• A. Both (A) and (R) are true and (R) is the correct explanation of (A).
• B. Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
• C. (A) is true but (R) is false.
• D. (A) is false but (R) is true.

Hint:

Think about what fills the spaces between individual kernels when grain is stored in bulk.

Answer 1

The Correct Option is A

Consider heat trying to flow through two different arrangements of the same grain. In the first, it moves through one solid kernel. In the second, it moves through many kernels with air trapped between them, as happens in bulk storage.

Since air has a much lower thermal conductivity than the grain material, every air gap the heat has to cross in the bulk case acts like extra resistance.

\[k_{air} \ll k_{grain} \Rightarrow k_{bulk} \lt k_{single \, grain}\]

This directly matches Assertion (A), and Reason (R) states the exact cause, the low conductivity of air, so (R) explains (A) correctly.

\[\boxed{\text{Option 1: Both true, R explains A}}\]