The rate of cooling is constant still milk attains the temperature of the surrounding.
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B)
The temperature of milk falls off exponentially with time
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C)
While cooling, there is a flow of heat from milk to the surrounding as well as from surrounding to the milk but the net flow of heat is from milk to the surrounding and that is why it cools.
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D)
All three phenomenon, conduction, convection and radiation are responsible for the loss of heat from milk to the surroundings.
A ring consisting of two parts ADB and ACB of same conductivity k carries an amount of heat H. The ADB part is now replaced with another metal keeping the temperatures \[{{T}_{1}}\] and \[{{T}_{2}}\] constant. The heat carried increases to 2H. What should be the conductivity of the new ADB part? Given \[\frac{ACB}{ADB}=3\].
Direction: In the following questions, more than one of one answers given are correct. Select the correct answers and mark it according to the following codes:
Two bodies A and B have thermal emissivities of 0.01 and 0.81 respectively. The outer surface areas of the two bodies are the some. The two bodies emit total radian power at the same rate. The wavelength \[{{\lambda }_{B}}\] corresponding to maximum spectral radiancy in the radiation from B is shifted from the wa9.-velength corresponding to maximum spectral radiancy in the radiation from A, by \[1.00\,\mu m\]. If the temperature of A is 5802 K
Direction: In the following questions, more than one of one answers given are correct. Select the correct answers and mark it according to the following codes:
A cane is taken out from a refrigerator at \[0{}^\circ C\]. The atmospheric temperature is \[25{}^\circ C\]. If \[{{t}_{1}}\] is the time taken to heat from \[0{}^\circ C\] to \[5{}^\circ C\] and \[{{t}_{2}}\] is the time taken from \[10{}^\circ C\] to \[15{}^\circ C,\] then the wrong statements are to \[{{15}^{o}}C,~\] then the wrong statements are
Direction: In the following questions, more than one of one answers given are correct. Select the correct answers and mark it according to the following codes:
The rate of loss of heat from a body cooling under conditions of forced convection is proportional to its
(1) surface area
(2) excess of temperature over that of surrounding
Direction: Consider a spherical body A of radius R which placed concentrically in a hollow enclosure H, of radius 4R as shown in the figure. The temperature of the body A and H are \[{{T}_{A}}\] and \[{{T}_{H}},\] respectively.
Emissivity, transitivity and reflectivity of two bodies A and H are \[\text{(}{{e}_{A}},\text{ }{{e}_{H}})\text{ (}{{t}_{A}},\text{ }{{t}_{H}}\text{)}\] and \[({{r}_{A}},\text{ }{{r}_{H}})\] respectively.
For answering following questions assume no absorption of the thermal energy by the space in-between the body and enclosure as well as outside the enclosure and all radiations to be emitted and absorbed normal to the surface.
The temperature of A (a perfect black body) is \[{{T}_{A}}=300K\] and temperature of H is \[{{T}_{0}}=OK\]. For H take \[{{e}_{H}}=0.5\] and \[t=0.5\]. For this situation mark out the correct statement(s).
A)
The rate at which A loses the energy is \[\beta J{{s}^{-1}}\]
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B)
The rate at which spherical surface containing P receives the energy is \[\frac{\beta }{2}J{{s}^{-1}}\].
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C)
The rate at which spherical surface containing Q receives the energy is \[\beta \,J/{{s}^{-1}}\]
Direction: Consider a spherical body A of radius R which placed concentrically in a hollow enclosure H, of radius 4R as shown in the figure. The temperature of the body A and H are \[{{T}_{A}}\] and \[{{T}_{H}},\] respectively.
Emissivity, transitivity and reflectivity of two bodies A and H are \[\text{(}{{e}_{A}},\text{ }{{e}_{H}})\text{ (}{{t}_{A}},\text{ }{{t}_{H}}\text{)}\] and \[({{r}_{A}},\text{ }{{r}_{H}})\] respectively.
For answering following questions assume no absorption of the thermal energy by the space in-between the body and enclosure as well as outside the enclosure and all radiations to be emitted and absorbed normal to the surface.
Direction: Consider a spherical body A of radius R which placed concentrically in a hollow enclosure H, of radius 4R as shown in the figure. The temperature of the body A and H are \[{{T}_{A}}\] and \[{{T}_{H}},\] respectively.
Emissivity, transitivity and reflectivity of two bodies A and H are \[\text{(}{{e}_{A}},\text{ }{{e}_{H}})\text{ (}{{t}_{A}},\text{ }{{t}_{H}}\text{)}\] and \[({{r}_{A}},\text{ }{{r}_{H}})\] respectively.
For answering following questions assume no absorption of the thermal energy by the space in-between the body and enclosure as well as outside the enclosure and all radiations to be emitted and absorbed normal to the surface.
Consider two cases, first one in which A is a perfect black body and the second in which A is a non-black body. In both the cases, temperature of body A is same equal to 300K and H is at temperature 600K. For H, \[t=0\] and \[a\ne 1\]. For this situation, mark out the correct statement.
A)
The bodies lose their distinctiveness inside the enclosure and both of them emit the same radiation as that of the black body.
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B)
The rate of heat loss by A in both cases is the same and is equal to\[\beta \,J{{s}^{-1}}\].
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C)
The rates of heat loss by A in both the cases are different.
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D)
From this information we can calculate exact rate of heat loss by A in different cases.