JEE Main202131 Aug 2021Evening ShiftPhysicsThermal Properties of MatterActual
Two thin metallic spherical shells of radii r 1 and r 2 r 1 < r 2 are placed with their centres coinciding. A material of thermal conductivity K is filled in the space between the shells. The inner shell is maintained at temperature θ 1 and the outer shell at temperature θ 2 θ 1 < θ 2 . The rate at which heat flows radially through the material is :
Options
- AK θ 2 - θ 1 r 2 - r 1
- BK θ 2 - θ 1 r 2 - r 1 4 π r 1 r 2
- Cπ K r 1 r 2 θ 2 - θ 1 r 2 - r 1
- D4 π K r 1 r 2 θ 2 - θ 1 r 2 - r 1
Correct answer
D. 4 π K r 1 r 2 θ 2 - θ 1 r 2 - r 1
Step-by-step solution
Equivalent resistance ( R ) = r 2 - r 1   K 4 π r 2 r 1 Thus, Heat flow = 4 π K r 1 r 2 θ 2 - θ 1 r 2 - r 1