NHPC JE'21 ME: Daily Practices Quiz. 26-Oct-2021

Quiz: Mechanical Engineering
Exam: NHPC
Topic: Thermodynamics

Each question carries 1 mark
Negative marking: 1/4 mark
Time: 6 Minutes

Q1. Which one of the following is not intensive property of the system?
(a) Volume
(b) Pressure
(c) Temperature
(d) Density

Q2. Which of the following is an example of irreversible process?
(a) Polytropic expansion of fluid
(b) Unrestricted expansion of gases
(c) Isothermal expansion
(d) Electrolysis

Q3. During throttling process
(a) Enthalpy does not change
(b) Pressure reduces
(c) Volume does not change
(d) Both (a) and (b)

Q4. If H be the heat supplied to the system to do work W and change in internal energy as ∆U, then,
(a) H = ∆U + W
(b) ∆U = H + W
(c) W = H + ∆U
(d) H = W/∆U

Q5. Which of the following devices complies with the Clausius statement of the second law of thermodynamics?
(a) Closed-cycle gas turbine
(b) Internal combustion engine
(c) Steam power plant
(d) Domestic refrigerator

Q6. Superheating of the steam is done at
(a) Constant temperature
(b) Constant volume
(c) Constant pressure
(d) Constant entropy

Solutions

S1. Ans. (a)
Sol. The property which is not intensive means it is extensive.
So, volume is extensive property.
Extensive Property: The property which does depends on the amount of matter contain in the system

S2. Ans. (b)
Sol. Irreversible process: It is actual process and on P-V diagram or T-S diagram or on any thermodynamics diagram it is not represented by a continuous line.
So, Unrestricted expansion of gases is an irreversible process.

S3. Ans. (d)
Sol. Throttling process is used to reduce pressure of fluid from higher pressure to lower pressure by keeping enthalpy constant.

S4. Ans. (a)
By First law of thermodynamics, the change in internal energy is equal to Heat added minus work by the system.
It also states that energy must be conserved for any system.

S5. Ans. (d)
Sol. Clausius statement: It is impossible to construct a cyclic device which works on a cycle and produce no other effect other than heat transfer from a cold body to a hot body.
Heat Pump and Refrigerator work on Clausius statement of second law of thermodynamics.

S6. Ans. (c)
Sol. Superheating of the steam is done at constant pressure.