Question

Doubling the thickness of a slab (same material) will make conductive heat transfer rate:

• A. Double
• B. Half
• C. Four times
• D. Zero

Hint:

Heat conduction $\propto \frac{1}{\text{thickness}}$. Increase thickness → decrease heat flow.

Answer 1

The Correct Option is B

Concept: Heat conduction through a slab is governed by Fourier’s law: \[ Q = \frac{kA(T_1 - T_2)}{L} \] where:
• $Q$ = heat transfer rate
• $k$ = thermal conductivity
• $A$ = area
• $L$ = thickness

Step 1: Understanding relationship.
From the formula: \[ Q \propto \frac{1}{L} \]

Step 2: Effect of doubling thickness.
If thickness becomes $2L$: \[ Q_{new} = \frac{kA(T_1 - T_2)}{2L} \]

Step 3: Comparing with original. \[ Q_{new} = \frac{Q}{2} \]

Step 4: Evaluating options.
• Double — Incorrect
• Half — Correct
• Four times — Incorrect
• Zero — Incorrect Final Conclusion:
Doubling thickness reduces heat transfer rate to half. Hence, option (2) is correct.