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Mechanical Engineering Objective Questions and Answers
A mechanical engineer is the person who designs, develops and builds machines. He also supervises production in manufacturing industries. A mechanical engineer is involved in the design of products to ensure that they are safe and efficient. The main areas of work for a mechanical engineer include engine design, aeronautics, robotics, surgical equipment and machine tool design among others. Mechanical engineers may also be involved in maintenance or service engineering.
Nowadays many people want to become Mechanical Engineers but they don’t know how to ace the interview. If you’re thinking of majoring in this field, then you’ll want to get familiar with what mechanical engineers do. Here are some of the most common questions people ask about this field.
Are you looking for Mechanical Engineering Objective Questions and Answers? This blog will provide complete set of objective type questions with answers.
1. The impact strength of an material is an index of its | Mechanical Engineering Objective
a. Toughness
b. Tensile strength
c. Capability of being cold worked
d. Hardness
e. Fatigue strength
Answer:
Toughness
2. If a material expands freely due to heating, it will develop | Mechanical Engineering Online Test
a. Thermal stress
b. Tensile stress
c. Bending
d. Compressive stress
e. No stress
Answer:
No stress
3. Ductility of material can be defined as | Mechanical Engineering Test Questions
a. Ability to undergo large permanent deformation in compression
b. Ability to recover its original form
c. Ability to undergo large permanent deformation in tension
d. All of the above
e. None of the above
Answer:
Ability to undergo large permanent deformation in compression
4. Cast iron is characterized by minimum of following % of carbon | Free Mechanical Reasoning Test
a. 0.2%
b. 0.8%
c. 1.3%
d. 2%
e. None of the above
Answer:
2%
5. Inconel is an alloy of | Mechanical Engineering Objective
a. Nickel, chromium and iron
b. Nickel and copper
c. Nickel and chromium
d. Nickel and zinc
e. Nickel and lead
Answer:
Nickel, chromium and iron
6. Which of the following processes is irreversible process | Mechanical Engineering Online Test
a. Isothermal
b. Adiabatic
c. Throttling
d. All of the above
Answer:
c. Throttling
Explanation:
In throttling process,
- No change in enthalpy from state one to state two (h1=h2)
- No work is done (W=0)
- Process is called isenthalpic
- Process is adiabatic (Q=0)
7. Which of the following processes are thermodynamically reversible? | Mechanical Engineering Test Questions
a. Throttling
b. Free expansion
Constant volume and constant pressure
d. Isothermal and adiabatic
Answer:
d. Isothermal and adiabatic
Explanation:
Throttling, Free expansion, Constant volume and Constant pressure processes and adiabatic process are thermodynamically irreversible whereas isothermal and adiabatic processes are thermodynamically reversible.
8. The instrument which measures the temperature of the source without direct contact is | Free Mechanical Reasoning Test
a. Bi-metallic cut out
b. Vapour pressure thermometer
c. Pyrometer
d. Thin film thermometer
Answer:
c. Pyrometer
Explanation:
Pyrometer is a device use for measuring relatively high temperature, such as are encountered in furnace. Most pyrometer works by measuring radiation from the body whose temperature is to be measured. Radiation devices have the advantages of not touch the material being measured.
9. Identify Open system and Closed system from the following: | Mechanical Engineering Objective
a. Blood circulation and respiration in human body
b. Fuel system and radiator in cars
c. Air compressor and Boiler
d. Shell and Tube Heat exchanger and Blower
Answer:
c. Air compressor and Boiler
Explanation:
Air compressor is an open system and boiler comes under closed system (i.e. boiler is having closed chamber)
10. Which thermometer is independent of the substance or material used in its construction? | Mechanical Engineering Online Test
a. Mercury thermometer
b. Alcohol thermometer
c. Ideal gas thermometer
d. Resistance thermometer
Answer:
c. Ideal gas thermometer
Explanation:
Ideal gas thermometer is independent of the substance or material used in its construction.
11. For the quick response of a thermocouple | Mechanical Engineering Test Questions
a. Its wire diameter should be large
b. The convective heat transfer coefficient should be high
c. The specific heat should be high
d. The density should not be very small
Answer:
b. The convective heat transfer coefficient should be high
Explanation:
For the quick response of a thermocouple the convective heat transfer coefficient should be high.
12. The first law of thermodynamics was developed by | Free Mechanical Reasoning Test
a. Joule
b. Kelvin
c. Charles
d. Carnot
Answer:
a. Joule
Explanation:
The first law of thermodynamics was developed bu Joule.
First Law of Thermodynamics: When a closed system executes a complete cycle the sum of heat interactions is equal to the sum of work interaction.
Q1-2 + Q2-1 = W1-2 + W2-1
13. The short coming of first law of thermodynamics is | Mechanical Engineering Objective
a. Direction of process
b. Possibility of process
c. Quality of energy
d. Quantity of energy
Answer:
d. Quantity of energy
Explanation:
The short coming of first law of thermodynamics is quantity of energy. Whereas, the short coming of second law of thermodynamics is quality of energy.
14. Carnot cycle has maximum efficiency for | Mechanical Engineering Online Test
c. Reversible engine
d. Irreversible engine
Answer:
c. Reversible engine
Explanation:
According to the statement, Carnot cycle has maximum efficiency for reversible engine. The reversible engine will always have a greater efficiency than the irreversible.
15. Which of the following constituents of a fuel does not contribute to its calorific value on combustion? | Mechanical Engineering Test Questions
a. Carbon
b. Hydrogen
c. Sulphur
d. Nitrogen
Answer:
d. Nitrogen
16. Water vapour can be considered as Ideal Gas | Free Mechanical Reasoning Test
a. Never
b. Always
c. At high pressure
d. At low pressure
Answer:
d. At low pressure
Explanation:
At very low pressure and high temperature all gases and vapour approaches to ideal gas behaviour.
17. Most of the gases exhibit drop in temperature upon expansion. However, this may not be true in case of | Mechanical Engineering Objective
b. Oxygen
c. Hydrogen
d. Helium
Answer:
c. Hydrogen
Explanation:
In thermodynamics, the Joule – Thompson (Also known as the Joule – Kelvin effect or Kelvin – Joule effect) describes the temperature change of real gas or liquid when it is forced through a value or porous plug while keeping it insulated so that no heat is exchanged with the environment. This procedure is called as throttling process or Joule – Thompson process. At room temperature, all gases except hydrogen, helium, and neon cool upon expansion by the Joule – Thompson process when being throttled through an orifice, there three gases experience the same effect but only at lower temperature.
18. When the fuel is burned and water is released in the liquid phase, the heating value of fuel is called | Mechanical Engineering Online Test
a. Higher heating value
b. Lower heating value
c. Enthalpy of formation
d. None of the above
Answer:
a. Higher heating value
19. A fluid behave as an ideal gas provided it is at | Mechanical Engineering Test Questions
a. High temperature and pressure
b. High temperature and Moderate pressure
c. Low temperature and pressure
d. High temperature and low pressure
Answer:
d. High temperature and low pressure
Explanation:
A real gas obeys perfect gas law at high temperature and low pressure. Inter molecular attraction between molecules are negligible. Volume occupied by molecules as compared to total volume is negligible.
20. The effect of blade friction in a steam turbine is to | Free mechanical Reasoning Test
a. reheat the gas
b. increase the specific output
c. reduce the exhaust pressure
d. reduce work done
Answer:
d. reduce work done
Explanation:
Some resistance is always offered by the blade surface to the idling steam jet, whose effect is to reduce the velocity of the jet. The effect of blade friction in a steam turbine is to reduce the work done.
The blade friction in the impulse turbine reduces the velocity of steam by 10 to 15 % passes over the blade.
21. The process of maintaining the speed of the turbine constant for various load condition is | Mechanical Engineering Objective
a. Bleeding
b. Reheating
c. Governing
d. Compounding
Answer:
c. Governing
Explanation:
The process of maintaining the speed of the turbine constant for various load condition is governing.The throttle governing of a steam turbine is a method of controlling the turbine output by varying the quantity of steam entering into the turbine. This method is also known as servo motor method.
22. Turbine gives best performance (i.e. work at peak efficiency) when they are operated at full or design load. The performance of many turbines deteriorate considerably at part loads. Which of the following turbines is best suted for operate at part loads?
a. Pelton turbine
b. Francis turbine
c. Propeller turbine
d. Kaplan turbine
Answer:
d. Kaplan turbine
23. Bleeding in turbine means
a. Leakage of steam
b. Steam doing no useful work
c. Removal of condensed steam
d. Extracting steam for preheated feed water
Answer:
d. Extracting steam for preheated feed water
24. Why compounding of steam turbine is done? | Free Mechanical Reasoning Test
a. To improve efficiency
b. To reduce exit losses
c. To reduce rotor speed
d. All of the above
Answer:
c. To reduce rotor speed
25. A Nozzle device is used to convert the | Mechanical Engineering Objective
a. Total energy to pressure
b. Total energy to velocity
c. Kinetic energy to mechanical energy
d. Potential energy to kinetic energy
Answer:
b. Total energy to velocity
Explanation:
In nozzle area decreases, velocity increases and pressure decreases. Nozzle converts pressure energy into kinetic energy. Since the objective of the device is to increase the flow velocity.
26. The function of steam nozzle is to convert
a. heat energy of steam into kinetic energy
b. heat energy of steam into rotational energy
c. kinetic energy into heat energy of steam
d. heat energy of steam into pressure energy
Answer:
a. heat energy of steam into kinetic energy
Explanation:
A steam nozzle converts heat energy of steam into kinetic energy. The mass of steam, passing through any section of the nozzle remains constant, the variation of steam pressure in the nozzle depends upon the velocity, specific volume of any dryness fraction of steam. A well designed nozzle converts the heat energy of steam into kinetic energy with a minimum losses.
27. Shock effect in a nozzle is felt in
a. divergent portion
b. straight portion
c. convergent portion
d. throat
Answer:
a. divergent portion
Explanation:
Shock effect in a nozzle is felt in divergent portion. For a nozzle to have a supersonic outlet, the speed at the throat should be definitely sonic and the nozzle should be divergent from the throat section.
28. Speed of sound is maximum in | Free Mechanical Reasoning Test
a. Liquid
b. Gas
c. Solid
d. Semisolid
Answer:
c. Solid
Explanation:
Speed of the sound depends on the density of medium through which sound is travelling more. As density of solid is more than liquid and gases, sound travels with more speed in solids.
29. Convergent – divergent nozzle is said to be choked when | Mechanical Engineering Objective
a. critical pressure is attained at the exit and Mach number at this section is sonic
b. Velocity at the throat becomes supersonic
c. Exit velocity becomes supersonic
d. Mass flow rate through the nozzle reaches a maximum value
Answer:
d. Mass flow rate through the nozzle reaches a maximum value
Explanation:
Convergent – Divergent nozzle is said to be choked when mass flow rate through the nozzle reaches a maximum value.
30. Gas turbine blade material must possess
a. High creep rate
b. Low creep rate
c. Plasticity at high temperature
d. Electrical conductivity
Answer:
b. Low creep rate
Explanation:
Modern turbine blades often use nickel based super alloys that incorporate chromium, cobalt and rhenium.
Gas turbine blade material must posses following properties:
- Material must withstand high temperature and high stress
- It must have low creep rate
- It must have high resistance to oxidation corrosion and erosion
- It must neither be brittle at ordinary temperature nor plastic when hot
- It must have good cast ability or forge ability characteristics
- It must have good machine ability to achieve precise dimension
- It must have high resistance to fatigue failure
- It must maintain structural stability when exposed to varying temperature.
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the answer for ductility is : ability to undergo large permanent deformation in tension ( like drawing of thin wires)
though ductility and malleability are use synonymously, there is a small technical difference between them in that malleability is the ability to undergo large permanent deformation in compression ( like flattening of a metal to sheet)..
3. Ductility of material can be defined as
c. Ability to undergo large permanent deformation in tension
this is best answer i can prefer…