Thermal Properties Of Matter
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A black body at 1227°C emits radiations with maximum intensity at a wavelength of 5000 Å. If the temperature of the body is increased by 1000°C, the maximum intensity will be observed at
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4000 Å
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5000 Å
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6000 Å
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3000 Å
D.
3000 Å
The product of wavelength corresponding to maximum intensity of radiation and temperature of the body in Kelvin is constant.
According to Wien's law
where 
is wavelength corresponding to maximum intensity of radiation and T is temperature of the body in Kelvin.
Given, T = 1227 + 273 = 1500 K,
T' = 1227 + 1000 + 273 = 2500 K
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A black body is at 727o C. It emits energy at a rate which is proportional to:
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(727)2
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(1000)4
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(1000)2
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(727)2
B.
(1000)4
Amount of heat energy radiated per secnd by unit area of black body is directly proportional to fourth power of absoulte temperature.
Accordign to steafan's law,
Where σ is constatn of proportionality and called Steafan's constant. Its value is
5.67 x 10-8 Wm-2 K-4.
hence, E = (727+273)4
E = (1000)4
A block body t 227o C radiates heat at the rate of 7 cal cm-2 s-1. At a temperature of 727o C, the rate of heat radiated in the same units will be
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60
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50
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112
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80
C.
112
Apply Stefan's law of radiation.
A cylindrical metallic rod in thermal contact with two reservoirs of heat at its two ends conducts an amount of heat Q in time t. The metallic rod is melted and the material is formed into a rod of half the radius of the original rod. What is the amount of heat conducted by the new rod when placed in thermal contact with the two reservoirs in time t?
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Q/4
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Q/16
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2Q
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Q/2
B.
Q/16
In steady state, the amount of heat flowing from one face to the other face in time t is given by 
A gas mixture consists of 2 moles of O2 and 4 moles of Ar at temperature T. Neglecting all vibrational modes, the total internal energy of the system is
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4 RT
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15 RT
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9 RT
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11 RT
D.
11 RT
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