Previous Years GATE MCQ’s on Work, Heat and Power

Previous Year GATE Solved Questions on Work, Heat and Power

Question 1. A cyclic heat engine does 50 KJ of work per cycle. If the efficiency of the heat engine is 75 %, the heat rejected per cycle is

(A)

(B)

(C)

(D)

GATE-ME-2001

Hint 1. (Ans A)

Or, Net heat input ,

Also,

Therefore Net rejected heat,

Question 2. A Carnot cycle is having an efficiency of 0.75. If the temperature of the high temperature reservoir is 727°C, what is the temperature of the low temperature reservoir?

(A) 23 °C

(B) -23°C

(D) 250°C

GATE-ME-2002

Hint 2. (Ans B)

Therefore

Data for Q.3-4 are given below. Solve the problem and choose correct answer.

Nitrogen gas (molecular weight 28) is enclosed in a cylinder by a piston, at the initial condition of 2 bar, 298 K and 1 . In a particular process, the gas slowly expands under isothermal condition, until the volume becomes 2 .Heat exchange occurs with the atmosphere at 298 K during this process.

Question 3. The work interaction for the nitrogen gas is

(A) 200 KJ

(B) 138.6 KJ

(D) -200 KJ

GATE-ME-2003

Hint 3. (Ans B)

Work interaction,

Question 4. The entropy change for universe during the process in KJ/K is

(A) 0.4652

(B) 0.0067

(D) -0.06711

GATE-ME-2003

Hint 4. (Ans A)

For isothermal process,

Question 5. A gas contained in a cylinder is compressed, the work required for compression being 5000 KJ. During the process, heat interaction of 2000 KJ causes the surroundings to be heated. The change in internal energy of the gas during the process is

(A) -7000 KJ

(B) -3000KJ

(D) +7000 KJ

GATE-ME-2004

Hint 5. (Ans C)

Question 6. Match items from groups I,II, III, IV and V.

Group I	Group II	Group III	Group IV	Group V
	When added to the system, is	Differential	Function	Phenomenon
E Heat	G positive	I Exact	K Path	M Transient
F work	H Negative	J Inexact	L Point	N Boundary

(A) F-G-J-K-M

E-G-I-K-N

(B) E-G-I-K-M

F-H-I-K-N

E-H-I-L-M

(D) E-G-J-K-N

F-H-J-K-M

GATE-ME-2006

Hint 6. (Ans D)

When added to the system		Differential	Function	Phenomenon
Heat	Positive	Inexact	Path	Boundary
Work	Negative	Inexact	Path	Transient

Common Data Question: 7 & 8

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

Question 7. The above cycle is represented on T-S plane by

(A)

(B)

(C)

(D)

GATE-ME-2007

Hint 7. (Ans C)

Since 3-1 is adiabatic process, it will be represented by a straight line on T-s plane. 1-2 is isobaric process, so with decrease of volume, temperature will also decrease.

Question 8. If the specific heats of the working fluid are constant and the value of specific heat ratio 1.4, the thermal efficiency (%) of the cycle is

(A) 21

(B) 40.9

(D) 59.7

GATE-ME-2007

Hint 8. (Ans A)

Question 9. A heat transformer is a device that transfers a part of the heat, supplied to it at an intermediate temperature, to a high temperature reservoir while rejecting the remaining part to a low temperature heat sink. In such a heat transformer, 100 KJ of heat is supplied at 350 K. the maximum amount of heat in KJ that can be transferred to 400 K, when the rest is rejected to a heat sink at 300 K is

(A) 12.50

(B) 14.29

(D) 57.14

GATE-ME-2007

Hint 9. (Ans D)

Common data for Questions 10,11 and 12:

In the figure shown, the system is a pure substance kept in a piston cylinder arrangement. The system is initially a two phase mixture containing 1 kg of liquid and 0.3 kg of vapour at a pressure of 100 kPa. Initially, the piston rests on a set of stops , as shown in the figure. A pressure of 200 kPa is required to exactly balance the weight of the piston and the outside atmospheric pressure. Heat transfer takes place into the system until its volume increases by 50 %. Heat transfer to the system takes place in such a manner that the piston, when allowed to move, does so in a very slow (quasi-static/quasi-equilibrium) process. The thermal reservoir from which heat is transferred to the system has a temperature of 400°C. Average temperature of the system boundary can be taken as 175°C. The heat transferred to the system is 1 KJ, during which its entropy increase by 10 J/K.