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JEE Mains · Physics · STD 11 - 10.2 transmission of heat

A wire of length 10 cm and diameter 0.5 mm is used in a bulb. The temperature of the wire is \(1727^{\circ} \mathrm{C}\) and power radiated by the wire is 94.2 W. Its emissivity is \(\frac{x}{8}\) where \(x=\)_______
(Given \(\sigma=6.0 \times 10^{-8} \mathrm{~W} \mathrm{~m}^{-2} \mathrm{~K}^{-4}, \pi=3.14\) and assume that the emissivity of wire material is same at all wavelength.)

  1. A 10
  2. B 5
  3. C 15
  4. D 20
Verified Solution

Answer & Solution

Correct Answer

(B) 5

Step-by-step Solution

Detailed explanation

\(\mathrm{L}=10 \mathrm{~cm}, \mathrm{~d}=0.5 \mathrm{~mm}, \mathrm{~T}=1727^{\circ} \mathrm{C}=2000 \mathrm{~K}\) Power, \(\mathrm{P}=94.2 \mathrm{~W}\) \(\mathrm{P}=\varepsilon \sigma \mathrm{AT}^4\)…
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