ऊष्मा स्थानांतरण की कौन सी विधि में किसी भौतिक माध्यम की आवश्यकता नहीं होती है?

Which one of the following phenomena is primarily based on the process of convection?

The thermal resistance of a uniform conductor is:

Rods x and y of equal dimensions but of different materials are joined as shown in a linear arrangement (A-B-Junction-E-F). Temperatures of end points A and F are maintained at 100°C and 40°C respectively. Given that the thermal conductivity of rod x is three times that of rod y, and the center is split into parallel paths, the temperatures at junction points B and E are close to: