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 ( σ = Stefan's constant) (Assume that emissivity of wire material is same at all wavelength) (a) Pσ T⁴π d L (b) Pσ T²π d L (c) Pσ T²π d² L² (d) P²σ T⁴π d L

Answer: (a). Radiating area of the wire (curved surface) A = π d L. P = eσ A T⁴ = eσ π d L T⁴ e = (P)/(σ T⁴ π d L) So the answer is (a).

A wire of length L and diameter d is used in a bulb. The temperature… | MHT CET 2026 (11 Apr, Shift 1)

Q16MHT CET 2026 · 11 APR · SHIFT 1Medium

Thermal Radiation: Black Body, Stefan & Wien

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 ( $\sigma$ = Stefan's constant) (Assume that emissivity of wire material is same at all wavelength)

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Answer: (a)

Radiating area of the wire (curved surface) $A = \pi d L$ .
$P = e\sigma A T^4 = e\sigma \pi d L T^4$
$e = \dfrac{P}{\sigma T^4 \pi d L}$
So the answer is (a).

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Thermal Radiation: Black Body, Stefan & Wien question from MHT CET 2026 (11 Apr, Shift 1)

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