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
11
MCQ (Multiple Correct Answer)
Consider a heat engine as shown in figure. $Q_1$ and $Q_2$ are heat added both to $T_1$ and heat taken from $T_2$ in one cycle of engine. $W$ is the mechanical work done on the engine.
If W > 0, then possibilities are
A
$Q_1>Q_2>0$
B
$Q_2>Q_1>0$
C
$Q_2< Q_1<0$
D
$Q_1<0, Q_2>0$