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6
MCQ (Single Correct Answer)

Three copper blocks of masses $M_1, M_2$ and $M_3 \mathrm{~kg}$ respectively are brought into thermal contact till they reach equilibrium. Before contact, they were at $T_1, T_2, T_3\left(T_1>T_2>T_3\right)$. Assuming there is no heat loss to the surroundings, the equilibrium temperature $T$ is ( $s$ is specific heat of copper)

A
$T=\frac{T_1+T_2+T_3}{3}$
B
$T=\frac{M_1 T_1+M_2 T_2+M_3 T_3}{M_1+M_2+M_3}$
C
$T=\frac{M_1 T_1+M_2 T_2+M_3 T_3}{3\left(M_1+M_2+M_3\right)}$
D
$T=\frac{M_1 T_1 s+M_2 T_2 s+M_3 T_3 s}{M_1+M_2+M_3}$
7
MCQ (Multiple Correct Answer)

Which of the processes described below are irreversible?

A
The increase in temperature of an iron rod by hammering it
B
A gas in a small container at a temperature $T_1$ is brought in contact with a big reservoir at a higher temperature $T_2$ which increases the temperature of the gas
C
A quasi-static isothermal expansion of an ideal gas in cylinder fitted with a frictionless piston
D
An ideal gas is enclosed in a piston cylinder arrangement with adiabatic walls. A weight $w$ is added to the piston, resulting in compression of gas
8
MCQ (Multiple Correct Answer)

An ideal gas undergoes isothermal process from some initial state $i$ to final state $f$. Choose the correct alternatives.

A
$d U=0$
B
$d Q=0$
C
$d Q=d U$
D
$d Q=d W$
9
MCQ (Multiple Correct Answer)

Figure shows the $p-V$ diagram of an ideal gas undergoing a change of state from $A$ to $B$. Four different parts I, II, III and IV as shown in the figure may lead to the same change of state.

A
Change in internal energy is same in IV and III cases, but not in I and II
B
Change in internal energy is same in all the four cases
C
Work done is maximum in case I
D
Work done is minimum in case II
10
MCQ (Multiple Correct Answer)

Consider a cycle followed by an engine (figure.)

1 to 2 is isothermal

2 to 3 is adiabatic

3 to 1 is adiabatic

Such a process does not exist, because

A
heat is completely converted to mechanical energy in such a process, which is not possible
B
mechanical energy is completely converted to heat in this process, which is not possible
C
curves representing two adiabatic processes don't intersect
D
curves representing an adiabatic process and an isothermal process don't intersect
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