# Carnot Cycle

## Trending Questions

**Q.**A Carnot engine whose sink is at 300 K has an efficiency of 40%. By how much should the temperature of source be increased so as to increase its efficiency by 50% of original efficiency?

- 325 K
- 250 K
- 380 K
- 275 K

**Q.**An ideal Carnot engine whose efficiency is 40% receives heat at 500 K. If its efficiency were 50%, then in take temperature for same exhaust temperature would be

- 700 K
- 800 K
- 900 K
- 600 K

**Q.**A Carnot engine has efficiency of 50 %. If the temperature of sink is reduced by 40∘C, its efficiency increases by 30 %. The temperature of the source will be:

- 366.7 K
- 255.1 K
- 266.7 K
- 166.7 K

**Q.**The coefficient of performance of a refrigerator is 5. If the temperature inside freezer is −20∘C, the temperature of the surroundings to which it rejects heat is:

- 11∘C

- 21∘C

- 31∘C

- 41∘C

**Q.**

Write an expression for calculating the efficiency of a machine.

**Q.**Two Carnot engines A and B are operated in succession. The first one, A receives heat from a source at T1=800 K and rejects to a sink at T2 K. The second engine B receives heat rejected by the first engine and rejects to another sink at T3=300 K. Find the value of T2 if

(i) the work outputs of the two engines are equal.

(ii) the efficiencies of the two engines are equal.

**Q.**The coefficient of performance of a Carnot refrigerator working between 30∘C and 0∘C is

- 10
- 9
- 1
- 0

**Q.**A reversible engine converts one-sixth of the heat input into work. When the temperature of the sink is reduced by 62∘C, the efficiency of the engine is doubled. The temperatures of the source and sink are

- 99°C, 37°C
- 80°C, 37°C
- 95°C, 28°C
- 90°C, 37°C

**Q.**

The efficiency of the Otto cycle is given by which of these expressions?Where r = compression ratio.

1−1rγ−1

1−1γr−1

1r

1γ

**Q.**

Why is carnot cycle most efficient?

**Q.**The temperature of sink of Carnot engine is 27∘C. Efficiency of engine is 25%. Then temperature of source is

- 227
^{o }C - 327
^{o }C - 127
^{o }C - 27
^{o }C

**Q.**

A heat engine is involved with the exchange of heat of $1950J$, $-40J$, $+125J$ and $-QJ$, during one cycle achieving an efficiency of $50.0\%$. the value of $Q$ is:

$980J$

$640J$

$40J$

$400J$

**Q.**

What is the equivalent of 1 joule in calories?

**Q.**

How can we increase the efficiency of a heat engine?

**Q.**

A reversible heat engine converts one- fourth of the heat input into work. When the temperature of the sink is reduced by $52K$, its efficiency is doubled. The temperature in Kelvin of the source will be_______.

**Q.**

A 10
kW drilling machine is used to drill a bore in a small aluminium
block of mass 8.0 kg. How much is the rise in temperature of the
block in 2.5 minutes, assuming 50% of power is used up in heating the
machine itself or lost to the surroundings. Specific heat of
aluminium = 0.91 J g^{–1}
K^{–1}.

**Q.**

How do you increase Carnot efficiency?

**Q.**A Carnot engine whose source is at 400 K takes 200 cal of heat and rejects 150 cal to the sink. What is the temperature of the sink?

- cannot say
- 800 K
- 400 K
- 300 K

**Q.**

Two ideal Carnot engines operate in cascade (all heat given up by one engine is used by the other engine to produce work) between temperatures ${\mathrm{T}}_{1}$ and ${\mathrm{T}}_{2}$. The temperature of the hot reservoir of the first engine is ${\mathrm{T}}_{1}$ and the temperature of the cold reservoir of the second engine is ${\mathrm{T}}_{2}$. $\mathrm{T}$ is the temperature of the sink of first engine which is also the source for the second engine. How is $\mathrm{T}$ related to ${\mathrm{T}}_{1}$ and ${\mathrm{T}}_{2}$ if both the engines perform equal amount of work?

$\mathrm{T}=\frac{2{\mathrm{T}}_{1}{\mathrm{T}}_{2}}{({\mathrm{T}}_{1}+{\mathrm{T}}_{2})}$

$\mathrm{T}=\frac{{\mathrm{T}}_{1}+{\mathrm{T}}_{2}}{2}$

$\mathrm{T}=0$

$\mathrm{T}=\sqrt{{\mathrm{T}}_{1}{\mathrm{T}}_{2}}$

**Q.**What is the temperature of source in Carnot cycle of 10% efficiency when heat exhausts at 270 K?

- 400 K
- 500 K
- 600 K
- 300 K

**Q.**A thermodynamic cycle with an ideal gas as working fluid is shown below.

If the specific heats of the working fluid are constant and the value of specific heat ratio γ is 1.4, the thermal efficiency (in %) of the cycle is

- 21
- 42
- 2.1
- 0.21

**Q.**A carnot engine having an efficiency of η=15 is used as a heat engine. Now it is used as a refrigerator. If work done by compressor is 40 J, the amount of energy delivered to surroundings is

- 200 J
- 160 J
- 120 J
- 50 J

**Q.**A Carnot engine whose sink is at 300 K has an efficiency of 40%. By how much should the temperature of source be increased so as to increase its efficiency by 50% of original efficiency?

- 280 K
- 275 K
- 325 K
- 250 K

**Q.**

A Carnot engine absorbs an amount Q of heat from a reservoir at an abosolute temperature T and rejects heat to a sink at a temperature of T3. The amount of heat rejected is

*Q*/ 4*Q*/ 3*Q*/ 22

*Q*/ 3

**Q.**

What is the Industrial Unit of Power?

**Q.**

A Carnot's engine used first an ideal monoatomic gas then an ideal diatomic gas. If the source and sink temperature are 411∘C and 69∘Crespectively and the engine extracts 1000 J of heat in each cycle, then area enclosed by the PV diagram is

100

*J*300

*J*500

*J*700

*J*

**Q.**The temperature inside and outside of the refrigerator is 260 K and 315 K respectively. Assuming that the refrigerator cycle is reversible, calculate the heat delivered to the surroundings for every joule of work done.

- 5 J
- 5.73 J
- 6.19 J
- 5 J

**Q.**

In one cycle of the engine, the net change in the entropy of both reservoirs (hot and cold together) is:

zero

greater than or equal to zero

less than zero

depends on the type of engine

**Q.**Temperature of source is 330∘C. Temperature of sink is changed in order to increase the efficiency of engine from 15 to 14, by

- 30 K
- 303 K
- 603 K
- 60 K

**Q.**

Figure below represents a Carnot engine that works between temperatures T1 400 K and T2 150 K and drives aCarnot refrigerator that works between temperatures T3 325 K and T4 225 K.What is the ratio Q3Q1?

104/85

104/95

85/104

95/104