MHT CET202611 April 2026Morning ShiftPhysicsThermal Properties of MatterActual
A wire of length L and diameter d is used in a bulb. The temperature of wire is T and power radiated by the wire is P . Its emissivity is ( = Stefan's constant) (Assume that emissivity of wire material is same at all wavelength)
Options
- AP T^4 d L
- BP T^2 d L
- CP T^2 d^2 L^2
- DP^2 T^4 d L
Correct answer
A. P T^4 d L
Step-by-step solution
According to Stefan-Boltzmann law, the power radiated by a body is given by P = e A T^4 . For a cylindrical wire of length L and diameter d , the radiating surface area is A = d L . Substituting the area into the power equation gives P = e ( d L) T^4 . Rearranging for emissivity e , we get e = P T^4 d L . Answer: P T^4 d L