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Q. No.Two spherical bodies of same materials having radii \(0.2~ \text m\) and \(0.8~ \text m\) are placed in same atmosphere. The temperature of the smaller body is \(800 ~ K \) and temperature of the bigger body is \(400~ K\). If the energy radiated from the smaller body is \(E, \) the energy radiated from the bigger body is (assume, effect of the surrounding temperature to be negligible).
1. \(256 ~E\)
2. \(16 ~E\)
3. \(64~ E\)
4. \(E\)
1. \(256 ~E\)
2. \(16 ~E\)
3. \(64~ E\)
4. \(E\)
Subtopic: Â Radiation |
Level 4: Below 35%
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A wire of length \(10~\text{cm} \) and diameter \(0.5 \text{ mm} \) is used in a bulb. The temperature of the wire is \(1727^{\circ} \text{C}\) and power radiated by the wire \(94.2~\text{W}.\) Its emissivity is \(\dfrac{x}{8}\) then the value of \(x\) is:
(Given \(\sigma=6.0 \times 10^{-8}~ {\text{Wm}}^{-2} {~\text K}^{-4} , \pi=3.14 \) and assume that the emissivity of wire material is same at all)
1. \(5 \)
2. \(4\)
3. \(6\)
4. \(7\)
(Given \(\sigma=6.0 \times 10^{-8}~ {\text{Wm}}^{-2} {~\text K}^{-4} , \pi=3.14 \) and assume that the emissivity of wire material is same at all)
1. \(5 \)
2. \(4\)
3. \(6\)
4. \(7\)
Subtopic: Â Radiation |
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