The emissivity of tungsten is 0.400. a tungsten sphere with a radius of 1.45 cm is suspended within a large evacuated enclosure whose walls are at 320 k. what power input is required to maintain the sphere at a temperature of 3000 k if heat conduction along the supports is negligible?

4850.62 Watt

Explanation:

e = 0.4

radius, r = 1.45 cm = 0.0145 m

To = 320 K

T = 3000 k

According to the Stefan's Boltzmann law

Energy radiated per unit time is given by

where, σ is the Stefan's constant, A be the area of sphere and e be the emmisivity.

So, Power radiated is energy radiated per second

E = 4850.62 Watt

layer a is the exosphere and layer b is the thermosphere.   is the answer i think but i hope this .

i believe the answer is a