Q#1
The heat capacity of a body depends on(a) the heat given
(b) the temperature raised
(c) the mass of the body
(d) the material of the body.
Answer: (c), (d).
The heat capacity of a body is the amount of heat required by it to raise the temperature by a unit degree. But this amount of heat is proportional to the mass and specific heat of the material of the body. Hence options (c) and (d).
Q#2
The ratio of specific heat capacity to the molar heat capacity of a body
(a) is a universal constant
(b) depends on the mass of the body
(c) depends on the molecular weight of the body
(d) is dimensionless.
Answer: (c)
Specific heat capacity, s = Q/mT, and
Molecular heat capacity, C = Q/nT
where Q = heat energy, m = mass, T = temperature difference, n = number of moles. Hence,
s/C = n/m = n/nM = 1/M
M = molecular weight. So the ratio depends on the molecular weight of the body. The option (c).
Q#3
If heat is supplied to a solid, its temperature
(a) must increase
(b) may increase
(c) may remain constant
(d) may decrease.
Answer: (b), (c).
If heat is supplied to a solid then depending upon the conditions its temperature may increase or remain constant. If the solid is at its melting point then the temperature will remain constant if heat is supplied otherwise its temperature will rise. Its temperature will never decrease if heat is supplied. Hence options (b) and (c).
Q#4
The temperature of a solid object is observed to be constant during a period. In this period
(a) heat may have been supplied to the body
(b) heat may have been extracted from the body
(c) no heat is supplied to the body
(d) no heat is extracted from the body.
Answer: (a), (b).
When heat is supplied to a solid at its melting point, the temperature does not increase till all the solid is melted. This heat is used in changing the state of the solid and called "Latent heat". Hence option (a).
Similarly, midway during the melting of the solid if heat is extracted from it, the surrounding liquid starts freezing and the temperature of the solid does not fall till all the liquid is frozen. Hence the option (b).
There is another possibility for these two options to be true. If heat is supplied to the solid and by some arrangement, this heat is totally used to do work by the solid then the temperature will not change. Similarly, if heat is extracted from the solid and simultaneously the same amount of work is done on it then also the temperature will remain constant.
Since there is no condition given about the solid, only it is observed for a period, hence there is a possibility of no heat being supplied or extracted during this period. In my opinion options (c) and (d) are also true.
Q#5
The temperature of an object is observed to rise in a period. In this period
(a) heat is certainly supplied to it.
(b) heat is certainly not supplied to it
(c) heat may have been supplied to it
(d) work may have been done on it.
Answer: (c), (d).
The temperature of an object may rise either due to the heat supplied or due to work being done on it. Hence the options (c) and (d).
Q#6
Heat and work are equivalent. This means
(a) when we supply heat to a body we do work on it.
(b) when we do work on a body we supply heat to it
(c) the temperature of a body can be increased by doing work on it
(d) a body kept at rest may be set into motion along a line by supplying heat to it.
Answer: (c)
Supplying heat to a body does not mean we do work on it, neither the body at rest can be set in motion by just supplying heat to it. The options (a) and (d) are not true. Also if we do work on a body its temperature may increase just like supplying heat {option (c) is correct, and means equivalence of heat and work} but it does not mean that we supply heat to it. Option (b) is also incorrect.
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