Two parallel disks of diameter d 5 0.6 m separated by l 5 0.4 m are located directly on top of each other. both disks are black and are maintained at a temperature of 450 k. the back sides of the disks are insulated, and the environment that the disks are in can be considered to be a blackbody at 300 k. determine the net rate of radiation heat transfer from the disks to the environment.

To solve this problem it is necessary to apply the concepts related to the Stefan-Boltzmann law which establishes that a black body emits thermal radiation with a total hemispheric emissive power (W / m²) proportional to the fourth power of its temperature.

Heat flow is obtained as follows:

Where,

F =View Factor

A = Cross sectional Area

Stefan-Boltzmann constant

T= Temperature

Our values are given as

D = 0.6m

The view factor between two coaxial parallel disks would be

Then the view factor between base to top surface of the cylinder becomes . From the summation rule

Then the net rate of radiation heat transfer from the disks to the environment is calculated as

Therefore the rate heat radiation is 780.76W

your answer is c! hope this : )

force required to detach it is given by

charges are taken to be fundamental charge

now we have

so above is the minimum distance at which it will detach