IES Conventional question paper with solution

IES Conventional question paper with solution (2000- 2014)

Download this link

DOWNLOAD

Thermodynamics mcq - Competitive Exams

The processes occuring in open system which permit the transfer of mass to and from the system, are known as A. flow processes B. non-flow processes C. adiabatic processes D. none of these Answer & Explanation Answer: Option A An open system is one in which A. heat and work crosses the boundary of the system, but the mass of the working substance does not crosses the boundary of the system B. mass of the working substance crosses the boundary of the system but the heat and work does not crosses the boundary of the system C. both the heat and work as well as mass of the working substance crosses the boundary of the system D. neither the heat and work nor the mass of the working substance crosses the boundary of the system Answer & Explanation Answer: Option C An isothermal process is governed by A. Boyle's law B. Charles' law C. Gay-Lussac law D. Avogadro's law Answer & Explanation Answer: Option A Workdone in a free expansion process is A. zero B. minimum C. maximum D. positive Answer & Explanation Answer: Option A An adiabatic process is one in which A. no heat enters or leaves the gas B. the temperature of the gas changes C. the change in internal energy is equal to the mechanical workdone D. all of the above Answer & Explanation Answer: Option D The amount of heat required to raise the temperature of the unit mass of gas through one degree at constant volume, is called A. specific heat at constant volume B. specific heat at constant pressure C. kilo Joule D. none of these Answer & Explanation Answer: Option A The ratio of specific heat at constant pressure (cp) and specific heat at constant volume (cv) is A. equal to one B. less than one C. greater than one D. none of these Answer & Explanation Answer: Option C If the value of n = 0 in the equation pvn = C, then the process is called A. constant volume process B. adiabatic process C. constant pressure process D. isothermal process Answer & Explanation Answer: Option C A process, in which the temperature of the working substance remains constant during its expansion or compression, is called A. isothermal process B. hyperbolic process C. adiabatic process D. polytropic process Answer & Explanation Answer: Option A When the gas is cooled at constant pressure, A. its temperature increases but volume decreases B. its volume increases but temperature decreases C. both temperature and volume increases D. both temperature and volume decreases Answer & Explanation Answer: Option D Workdone during adiabatic expansion is given by (where p1 v1, T1 = Pressure, volume and temperature for the initial condition of gas, p2, v2, T2 = Corresponding values for the final condition of gas, R = Gas constant, and γ = Ratio of specific heats) A. B. C. D. all of these Answer & Explanation Answer: Option D In a free expansion process, A. W1 - 2 = 0 B. Q1 - 2 = 0 C. dU = 0 D. all of these Answer & Explanation Answer: Option D The increase in entropy of a system represents A. increase in availability of energy B. increase in temperature C. decrease in pressure D. degradation of energy Answer & Explanation Answer: Option D The heat absorbed during a polytropic process is A.  x Workdone B. C. D. all of these Answer & Explanation Answer: Option D The sum of internal energy (U) and the product of pressure and volume (p.v) is known as A. workdone B. entropy C. enthalpy D. none of these Answer & Explanation Answer: Option C The value of gas constant (R) in S. I. units is A. 0.287 J/kgK B. 2.87 J/kgK C. 28.7 J/kgK D. 287 J/kgK Answer & Explanation Answer: Option D When two bodies are in thermal equilibrium with a third body, they are also in thermal equilibrium with each other. This statement is called A. Zeroth law of thermodynamics B. First law of thermodynamics C. Second law of thermodynamics D. Kelvin Planck's law Answer & Explanation Answer: Option A The measurement of a thermodynamic property known as temperature is based on A. Zeroth law of thermodynamics B. First law of thermodynamics C. Second law of thermodynamics D. none of these Answer & Explanation Answer: Option A The general gas energy equation is (where Q1 - 2 = Heat supplied, dU = Change in internal energy, and W1 - 2 = Work done in heat units) A. Q1 - 2 = dU + W1 - 2 B. Q1 - 2 = dU - W1 - 2 C. Q1 - 2 = dU/W1 - 2 D. Q1 - 2 = dU x W1 - 2 Answer & Explanation Answer: Option A Which of the following is the correct statement of the second law of thermodynamics? A. It is impossible to construct an engine working on a cyclic process, whose sole purpose is to convert heat energy into work. B. It is impossible to transfer heat from a body at a lower temperature to a higher temperature, without the aid of an external source. C. There is a definite amount of mechanical energy, which can be obtained from a given quantity of heat energy. D. all of the above Answer & Explanation Answer: Option D According to Kelvin-Planck's statement of second law of thermodynamics, A. it is impossible to construct an engine working on a cyclic process, whose sole purpose is to convert heat energy into work B. it is possible to construct an engine working on a cyclic process, whose sole purpose is to convert heat energy into work C. it is impossible to construct a device which operates in a cyclic process and produces no effect other than the transfer of heat from a cold body to a hot body D. none of the above Answer & Explanation Answer: Option A Kelvin-Planck's law deals with A. conservation of work B. conservation of heat C. conversion of heat into work D. conversion of work into heat Answer & Explanation Answer: Option C During which of the following process does heat rejection takes place in Carnot cycle? A. Isothermal expansion B. Isentropic expansion C. Isothermal compression D. Isentropic compression Answer & Explanation Answer: Option C A cycle consisting of one constant pressure, one constant volume and two isentropic processes is known as

A. Carnot cycle B. Stirling cycle C. Otto cycle D. Diesel cycle Answer & Explanation Answer: Option D

When the expansion or compression takes place according to the law pvn = C, the process is known as A. isothermal process B. adiabatic process C. hyperbolic process D. polytropic process Answer & Explanation Answer: Option D The general law of expansion or compression is pvn = C, The process is said to be hyperbolic, if n is equal to A. 0 B. 1 C. γ D. ∝ Answer & Explanation Answer: Option B A process, in which the gas is heated or expanded in such a way that the product of its pressure and volume remains constant, is called A. isothermal process B. hyperbolic process C. adiabatic process D. polytropic process Answer & Explanation Answer: Option B The entropy may be expressed as a function of A. pressure and temperature B. temperature and volume C. heat and work D. all of these Answer & Explanation Answer: Option A The polytropic index (n) is given by A. B. C. D. Answer & Explanation Answer: Option B In an irreversible process, there is a A. loss of heat B. no loss of heat C. gain of heat D. no gain of heat Answer & Explanation Answer: Option A The behaviour of super-heated vapour is similar to that of A. perfect gas B. air C. steam D. ordinary gas Answer & Explanation Answer: Option A If in the equation pvn = C, the value of n = ∝ , then the process is called A. constant volume process B. adiabatic process C. constant pressure process D. isothermal process Answer & Explanation Answer: Option A Carnot cycle has maximum efficiency for A. petrol engine B. diesel engine C. reversible engine D. irreversible engine Answer & Explanation Answer: Option C The efficiency of Carnot cycle depends upon A. temperature limits B. pressure ratio C. volume compression ratio D. cut-off ratio and compression ratio Answer & Explanation Answer: Option A The efficiency of the Carnot cycle may be increased by A. increasing the highest temperature B. decreasing the highest temperature C. increasing the lowest temperature D. keeping the lowest temperature constant Answer & Explanation Answer: Option A Otto cycle consists of A. two constant volume and two isentropic processes B. two constant pressure and two isentropic processes C. two constant volume and two isothermal processes D. one constant pressure, one constant volume and two isentropic processes Answer & Explanation Answer: Option A Which of the following represents Otto cycle on temperature - entropy (T - s) diagram?

A. B. C. D. Answer & Explanation Answer: Option C

The compression ratio for petrol engines is

A. 3 to 6 B. 5 to 8 C. 15 to 20 D. 20 to 30 Answer & Explanation Answer: Option B

The efficiency of Diesel cycle approaches to Otto cycle efficiency when

A. cut-off is increased B. cut-off is decreased C. cut-off is zero D. cut-off is constant Answer & Explanation Answer: Option C

The efficiency of Diesel cycle increases with

A. decrease in cut-off B. increase in cut-off C. constant cut-off D. none of these Answer & Explanation Answer: Option A

When cut-off ratio is __________ the efficiency of Diesel cycle approaches to Otto cycle efficiency.

A. zero B. 1/5 C. 4/5 D. 1 Answer & Explanation Answer: Option A

The compression ratio for Diesel engines is

A. 3 to 6 B. 5 to 8 C. 15 to 20 D. 20 to 30 Answer & Explanation Answer: Option C

For the same maximum pressure and temperature, A. Otto cycle is more efficient than Diesel cycle B. Diesel cycle is more efficient than Otto cycle C. Dual cycle is more efficient than Otto and Diesel cycles D. Dual cycle is less efficient than Otto and Diesel cycles Answer & Explanation Answer: Option B Otto cycle efficiency is higher than Diesel cycle efficiency for the same compression ratio and heat input because in Otto cycle

A. combustion is at constant volume B. expansion and compression are isentropic C. maximum temperature is higher D. heat rejection is lower Answer & Explanation Answer: Option D

Otto cycle is also known as

A. constant pressure cycle B. constant volume cycle C. constant temperature cycle D. constant temperature and pressure cycle Answer & Explanation Answer: Option B

The efficiency of Diesel cycle depends upon

A. temperature limits B. pressure ratio C. compression ratio D. cut-off ratio and compression ratio Answer & Explanation Answer: Option D

The compression ratio is the ratio of

A. swept volume to total volume B. total volume to swept volume C. swept volume to clearance volume D. total volume to clearance volume Answer & Explanation Answer: Option D