Question

In which one of the following materials the heat energy propagation is minimum due to conduction heat transfer?

• A. Lead
• B. Copper
• C. Water
• D. Air

Hint:

Materials with lower thermal conductivity transfer heat less effectively. Air has the lowest conductivity among the given materials.

Answer 1

The Correct Option is D

Step 1: Understand heat transfer by conduction.
The rate of heat transfer by conduction is given by Fourier's law: \[ Q = \frac{kA(T_1 - T_2)}{L} \] Where:
- \( Q \) is the rate of heat transfer,
- \( k \) is the thermal conductivity of the material,
- \( A \) is the area through which heat flows,
- \( T_1 - T_2 \) is the temperature difference,
- \( L \) is the thickness of the material.
Step 2: Analyze thermal conductivities of the materials.
- Lead has a high thermal conductivity (\( k = 35 \, \text{W/m·K} \)),
- Copper has an even higher thermal conductivity (\( k = 400 \, \text{W/m·K} \)),
- Water has a moderate thermal conductivity (\( k = 0.6 \, \text{W/m·K} \)),
- Air has the lowest thermal conductivity (\( k = 0.025 \, \text{W/m·K} \)).
Step 3: Conclusion
Since air has the lowest thermal conductivity, it will have the minimum heat propagation through conduction. Final Answer: \[ \boxed{\text{Air}} \]