Previous Year Papers

Download Solved Question Papers Free for Offline Practice and view Solutions Online.

Test Series

Take Zigya Full and Sectional Test Series. Time it out for real assessment and get your results instantly.

Test Yourself

Practice and master your preparation for a specific topic or chapter. Check you scores at the end of the test.

31.
A Carnot engine operating between temperatures T₁ and T₂ has efficiency 0.2. When T₂ is reduced by 50 K, its efficiency increases to 0.4. Then, T₁ and T₂ are respectively

200 K, 150 K

250 K, 200 K

300 K, 250 K

300 K, 200 K

250 K, 200 K

By Carnot's ideal heat engine

$η = 1 - \frac{T_{2}}{T_{1}}$

where, $η_{1} = 0.2, η_{2} = 0.4$

For the first condition

$η_{1} = 1 - \frac{T_{2}}{T_{1}} 0.2 = 1 - \frac{T_{2}}{T_{1}} or 0.2 = \frac{T_{1} - T_{2}}{T_{1}} . . . . . . . . . (i)$

For the second condition,

$η_{2} = 1 - \frac{T_{2} - 50}{T_{1}} 0.4 = \frac{T_{1} - (T_{2} - 50)}{T_{1}} 0.4 = \frac{T_{1} - T_{2} + 50}{T_{1}} 0.4 = \frac{T_{1} - T_{2}}{T_{1}} + \frac{50}{T_{1}} [From Eq . (i)] 0.4 - 0.2 = \frac{50}{T_{1}} T_{1} = \frac{50}{0.2} T_{1} = 250 K$

Putting the value of T₁ in Eq. (i), we get

$0.2 = \frac{T_{1} - T_{2}}{T_{1}} T_{2} = T_{1} - 0.2 T_{1} T_{2} = 250 - 0.2 \times 250 T_{2} = 250 - 50 T_{2} = 200 K So, T_{1} = 250 K, T_{2} = 200 K$

32.

If the temperatures of source and sink of a Carnot engine having efficiency η are each decreased by 100 K, then the efficiency

remains constant
becomes 1
decreases
increases

33.

The p-V diagram of a gas system undergoing cyclic process is shown here. The work done during isobaric compression is

100 J
200 J
400 J
500 J

34.

In a cyclic process, the amount of heat given to a system is equal to

net increase in internal energy
net work done by the system
net decrease in internal energy
net change in volume

35.

Identify the wrong statement

For isothermal process, ΔT = 0
For isochoric process, ΔV = 0
For cyclic process, ΔW = 0
For adiabatic process, ΔQ = 0

36.

A Carnot engine whose efficiency is 40%, receives heat at 500 K. If the efficiency is to be 50%, the source temperature for the same exhaust temperature is

900 K
600 K
700 K
800 K

37.

The thermodynamic process in which no work is done on or by the gas is

isothermal process
adiabatic process
isochoric process
isobaric process

38.

A refrigerator with coefficient of performance $\frac{1}{3}$ releases 200 J of heat to a hot reservoir. Then the work done on the working substance is

$\frac{100}{3} J$
100 J
$\frac{200}{3} J$
150 J

39.

The heat capacity per mole of water is (R is universal gas constant)

9 R
$\frac{9}{2} R$
6 R
5 R

40.

The change in internal energy of a given mass of gas, when its volume changes from V to 2V at constant pressure p is $(\frac{C_{p}}{C_{V}} = γ, universal gas constant = R)$