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question_answer1)
The length of the two rods made up of the same metal and having the same area of cross-section are 0.6 m and 0.8 m respectively. The temperature between the ends of first rod is \[{{90}^{o}}C\] and \[{{60}^{o}}C\]and that for the other rod is 150 and \[{{110}^{o}}C\]. For which rod the rate of conduction will be greater
A)
First done
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B)
Second done
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C)
Same for both done
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D)
None of the above done
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question_answer2)
The dimensions of thermal resistance are
A)
\[{{M}^{-1}}{{L}^{-2}}{{T}^{3}}K\] done
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B)
\[M{{L}^{2}}{{T}^{-2}}{{K}^{-1}}\] done
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C)
\[M{{L}^{2}}{{T}^{-3}}K\] done
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D)
\[M{{L}^{2}}{{T}^{-2}}{{K}^{-2}}\] done
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question_answer3)
The quantity of heat which crosses unit area of a metal plate during conduction depends upon
A)
The density of the metal done
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B)
The temperature gradient perpendicular to the area done
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C)
The temperature to which the metal is heated done
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D)
The area of the metal plate done
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question_answer4)
In order that the heat flows from one part of a solid to another part, what is required
A)
Uniform density done
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B)
Density gradient done
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C)
Temperature gradient done
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D)
Uniform temperature done
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question_answer5)
Two rods having thermal conductivity in the ratio of 5 : 3 having equal lengths and equal cross-sectional area are joined by face to face. If the temperature of the free end of the first rod is \[100{}^\circ C\] and free end of the second rod is \[{{20}^{o}}C\]. Then temperature of the junction is
A)
\[70{}^\circ C\] done
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B)
\[50{}^\circ C\] done
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C)
\[50{}^\circ C\] done
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D)
\[90{}^\circ C\] done
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question_answer6)
A wall has two layers A and B made of different materials. The thickness of both the layers is the same. The thermal conductivity of A and B are \[{{K}_{A}}\] and \[{{K}_{B}}\] such that \[{{K}_{A}}=3{{K}_{B}}\]. The temperature across the wall is \[20{}^\circ C\]. In thermal equilibrium
A)
The temperature difference across \[A=15{}^\circ C\] done
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B)
The temperature difference across \[A=5{}^\circ C\] done
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C)
The temperature difference across A is \[10{}^\circ C\] done
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D)
The rate of transfer of heat through A is more than that through B. done
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question_answer7)
Air is bad conductor of heat or partly conducts heat, still vacuum is to be placed between the walls of the thermos flask because
A)
It is difficult to fill the air between the walls of thermos flask done
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B)
Due to more pressure of air, the thermos can get crack done
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C)
By convection, heat can flow through air done
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D)
On filling the air, there is no advantage done
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question_answer8)
The rate of loss of heat from a body cooling under conditions of forced convection is proportional to its [A] heat capacity [B] surface area [C] absolute temperature [D] excess of temperature over that of surrounding : state if
A)
A, B, C are correct done
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B)
Only A and C are correct done
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C)
Only B and D are correct done
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D)
Only D is correct done
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question_answer9)
Which of the following is the correct device for the detection of thermal radiation
A)
Constant volume thermometer done
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B)
Liquid-in-glass thermometer done
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C)
Six's maximum and minimum thermometer done
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D)
Thermopile done
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question_answer10)
Good absorbers of heat are
A)
Poor emitters done
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B)
Non-emitters done
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C)
Good emitters done
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D)
Highly polished done
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question_answer11)
There is a rough black spot on a polished metallic plate. It is heated upto 1400 K approximately and then at once taken in a dark room. Which of the following statements is true
A)
In comparison with the plate, the spot will shine more done
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B)
In camparison with the plate, the spot will appear more black done
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C)
The spot and the plate will be equally bright done
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D)
The plate and the black spot can not be seen in the dark room done
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question_answer12)
A piece of blue glass heated to a high temperature and a piece of red glass at room temperature, are taken inside a dimly lit room then
A)
The blue piece will look blue and red will look as usual done
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B)
Red look brighter red and blue look ordinary blue done
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C)
Blue shines like brighter red compared to the red piece done
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D)
Both the pieces will look equally red. done
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question_answer13)
The wavelength of maximum emitted energy of a body at 700 K is 4.08 \[\mu m\]. If the temperature of the body is raised to 1400 K, the wavelength of maximum emitted energy will be
A)
\[1.02\ \mu m\] done
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B)
16.32\[\mu m\] done
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C)
8.16\[\mu m\] done
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D)
2.04\[\mu m\] done
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question_answer14)
On increasing the temperature of a substance gradually, which of the following colours will be noticed by you
A)
White done
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B)
Yellow done
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C)
Green done
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D)
Red done
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question_answer15)
The radiation energy density per unit wavelength at a temperature T has a maximum at a wavelength \[{{\lambda }_{0}}\]. At temperature \[2T\], it will have a maximum at a wavelength
A)
4\[{{\lambda }_{0}}\] done
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B)
2\[{{\lambda }_{0}}\] done
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C)
\[{{\lambda }_{0}}\]/2 done
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D)
\[{{\lambda }_{0}}\]/4 done
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question_answer16)
A metal ball of surface area \[200\ c{{m}^{2}}\] and temperature \[{{527}^{o}}C\] is surrounded by a vessel at \[{{27}^{o}}C\]. If the emissivity of the metal is 0.4, then the rate of loss of heat from the ball is \[(\sigma =5.67\times {{10}^{-8}}J/{{m}^{2}}\ -s-{{k}^{4}})\]
A)
108 joules approx. done
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B)
168 joules approx. done
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C)
182 joules approx. done
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D)
192 joules approx. done
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question_answer17)
The temperatures of two bodies A and B are \[{{727}^{o}}C\] and \[{{127}^{o}}C\]. The ratio of rate of emission of radiations will be
A)
727/127 done
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B)
625/16 done
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C)
1000/400 done
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D)
100/16 done
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question_answer18)
If the temperature of the sun (black body) is doubled, the rate of energy received on earth will be increased by a factor of
A)
2 done
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B)
4 done
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C)
8 done
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D)
16 done
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question_answer19)
Two spheres made of same material have radii in the ratio 1: 2 Both are at same temperature. Ratio of heat radiation energy emitted per second by them is
A)
1 : 2 done
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B)
1 : 8 done
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C)
1 : 4 done
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D)
1 : 16 done
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question_answer20)
A black body radiates energy at the rate of \[1\times {{10}^{5}}J/s\times {{m}^{2}}\] at temperature of \[227{}^\circ C\]. The temperature to which it must be heated so that it radiates energy at rate of \[1\times {{10}^{9}}J\text{/}s{{m}^{2}}\], is
A)
5000 K done
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B)
5000\[{}^\circ C\] done
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C)
500 K done
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D)
500\[{}^\circ C\] done
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question_answer21)
The ratio of radiant energies radiated per unit surface area by two bodies is 16 : 1, the temperature of hotter body is 1000K, then the temperature of colder body will be
A)
250 K done
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B)
500 K done
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C)
1000 K done
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D)
62.5 K done
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question_answer22)
In Newton's experiment of cooling, the water equivalent of two similar calorimeters is 10 gm each. They are filled with 350 gm of water and 300 gm of a liquid (equal volumes) separately. The time taken by water and liquid to cool from \[{{70}^{o}}C\] to \[{{60}^{o}}C\] is 3 min and 95 sec respectively. The specific heat of the liquid will be
A)
\[0.3\,Cal\text{/}gm\times {}^\circ C\] done
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B)
\[0.6\,Cal\text{/}gm\times {}^\circ C\] done
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C)
\[0.6\,Cal\text{/}gm\times {}^\circ C\] done
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D)
\[0.8\,Cal\text{/}gm\times {}^\circ C\] done
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question_answer23)
A container contains hot water at \[{{100}^{o}}C\]. If in time \[{{T}_{1}}\] temperature falls to \[{{80}^{o}}C\] and in time \[{{T}_{2}}\] temperature falls to \[{{60}^{o}}C\] from \[{{80}^{o}}C\], then
A)
\[{{T}_{1}}={{T}_{2}}\] done
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B)
\[{{T}_{1}}>{{T}_{2}}\] done
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C)
\[{{T}_{1}}<{{T}_{2}}\] done
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D)
None done
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question_answer24)
A body takes 5 minute to cool from \[80{}^\circ C\] to \[50{}^\circ C\]. How much time it will take to cool from \[60{}^\circ C\] to \[30{}^\circ C\], if room temperature is \[20{}^\circ C\].
A)
40 minute done
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B)
9 minute done
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C)
30 minute done
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D)
20 minute done
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question_answer25)
Two rods A and B are of equal lengths. Their ends are kept between the same temperature and their area of cross-sections are \[{{A}_{1}}\]and \[{{A}_{2}}\]and thermal conductivities \[{{K}_{1}}\] and \[{{K}_{2}}\]. The rate of heat transmission in the two rods will be equal, if
A)
\[{{K}_{1}}{{A}_{2}}={{K}_{2}}{{A}_{1}}\] done
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B)
\[{{K}_{1}}{{A}_{1}}={{K}_{2}}{{A}_{2}}\] done
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C)
\[{{K}_{1}}={{K}_{2}}\] done
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D)
\[{{K}_{1}}A_{1}^{2}={{K}_{2}}A_{2}^{2}\] done
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question_answer26)
Two identical plates of different metals are joined to form a single plate whose thickness is double the thickness of each plate. If the coefficients of conductivity of each plate are 2 and 3 respectively, then the conductivity of composite plate will be
A)
5 done
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B)
2.4 done
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C)
1.5 done
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D)
1.2 done
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question_answer27)
Two bars of thermal conductivities K and 3K and lengths \[1cm\] and \[2cm\] respectively have equal cross-sectional area, they are joined lengths wise as shown in the figure. If the temperature at the ends of this composite bar is \[{{0}^{o}}C\] and \[{{K}^{2}}/l\] respectively (see figure), then the temperature \[\varphi \]of the interface is
A)
\[{{50}^{o}}C\] done
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B)
\[\frac{100}{3}{{\ }^{o}}C\] done
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C)
\[{{60}^{o}}C\] done
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D)
\[\frac{200}{3}{{\ }^{o}}C\] done
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question_answer28)
The lengths and radii of two rods made of same material are in the ratios 1 : 2 and 2 : 3 respectively. If the temperature difference between the ends for the two rods be the same, then in the steady state, the amount of heat flowing per second through them will be in the ratio
A)
1: 3 done
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B)
4 : 3 done
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C)
8 : 9 done
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D)
3 : 2 done
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question_answer29)
Which of the following circular rods. (given radius r and length l) each made of the same material as whose ends are maintained at the same temperature will conduct most heat
A)
\[r=2{{r}_{0}};\ l=2{{l}_{0}}\] done
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B)
\[r=2{{r}_{0}};\ l={{l}_{0}}\] done
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C)
\[r={{r}_{0}};\ l={{l}_{0}}\] done
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D)
\[r={{r}_{0}};\ l=2{{l}_{0}}\] done
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question_answer30)
Mode of transmission of heat, in which heat is carried by the moving particles, is
A)
Radiation done
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B)
Conduction done
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C)
Convection done
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D)
Wave motion done
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question_answer31)
In which of the following process, convection does not take place primarily
A)
Sea and land breeze done
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B)
Boiling of water done
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C)
Warming of glass of bulb due to filament done
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D)
Heating air around a furnace done
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question_answer32)
A hot and a cold body are kept in vacuum separated from each other. Which of the following cause decrease in temperature of the hot body
A)
Radiation done
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B)
Convection done
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C)
Conduction done
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D)
Temperature remains unchanged done
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question_answer33)
A hot body will radiate heat most rapidly if its surface is
A)
White & polished done
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B)
White & rough done
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C)
Black & polished done
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D)
Black & rough done
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question_answer34)
If the temperature of the sun becomes twice its present temperature, then
A)
Radiated energy would be predominantly in infrared done
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B)
Radiated energy would be predominantly in ultraviolet done
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C)
Radiated energy would be predominantly in X-ray region done
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D)
Radiated energy would become twice the present radiated energy done
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question_answer35)
The maximum wavelength of radiations emitted at 900 K is \[4\mu m\]. What will be the maximum wavelength of radiations emitted at 1200 K
A)
\[3\mu m\] done
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B)
\[0.3\mu m\] done
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C)
\[1\mu m\] done
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D)
\[1\,\,m\] done
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question_answer36)
A black body radiates energy at the rate of \[E\] \[W\text{/}{{m}^{2}}\] at a high temperature TK. When the temperature is reduced to \[\frac{T}{2}K\], the radiant energy will be
A)
\[\frac{E}{16}\] done
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B)
\[\frac{E}{4}\] done
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C)
\[4E\] done
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D)
\[16E\] done
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question_answer37)
The radiant energy from the sun incident normally at the surface of earth is \[20\ kcal/{{m}^{2}}min\]What would have been the radiant energy incident normally on the earth, if the sun had a temperature twice of the present one
A)
\[160\ kcal/{{m}^{2}}\ min\] done
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B)
\[40\ kcal/{{m}^{2}}\ min\] done
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C)
\[320\ kcal/{{m}^{2}}\ min\] done
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D)
\[80\ kcal/{{m}^{2}}\ min\] done
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question_answer38)
Two black metallic spheres of radius 4m, at 2000 K and 1m at 4000 K will have ratio of energy radiation as
A)
1 : 1 done
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B)
4 : 1 done
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C)
1 : 4 done
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D)
2 : 1 done
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question_answer39)
Two spheres of same material have radius 1m and 4 m and temperature 4000K and 2000K respectively. The energy radiated per second by the first sphere is
A)
Greater than that by the second done
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B)
Less than that by the second done
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C)
Equal in both cases done
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D)
The information is incomplete done
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question_answer40)
A black body of surface area \[10\,c{{m}^{2}}\] is heated to \[127{}^\circ C\] and is suspended in a room at temperature \[27{}^\circ C\]. The initial rate of loss of heat from the body at the room temperature will be
A)
2.99 W done
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B)
1.89 W done
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C)
1.18 W done
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D)
0.99 W done
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