Hello friends, science lovers and fellow mechanical engineers, In today’s article I will discuss some important but most basic questions about mechanical engineering. After all this site is all about basic mechanical engineering, right ?? 😉 Its actually a small endeavor for the newly graduated engineers. I know it is arduous to get a good job just after having your BSc. degree. I am intending to write a series of articles regarding mechanical engineering interview questions and their answers. So let’s move on. :).
But first, have a look
some of the Basic Mechanical Engineering Questions with answers for your
written or interview exam preparation. These will be great for your viva
preparation as well.
Qn. What is Mechanical
Engineering?
Answer: Mechanical
Engineering is the branch of engineering which deals with the designing,
constructing, maintaining and manufacturing various mechanical systems.
Qn. What is the
difference between machine and engine?
Answer: Engine converts heat energy to Mechanical
Energy, but machine converts all forms of energy to mechanical energy except
heat energy.
Qn. What is
viscosity? What is Newton’s law of viscosity?
Answer: Viscosity is the property of the fluid which measures the
resistance of the fluid to the gradual deformation due to the shear stress.
Newtons Law of Viscosity states that: the shear stress on
the fluid is proportional to the velocity gradient.
Qn. What are
Newtonian and non-newtonian fluids ? Give examples.
Answer: Newtonian fluids follow the newtons law of viscosity and
non-newtonian fluids do not follow the law.
Examble :- Newtonian fluid: Water, air, etc. Non-Newtonian Fluid: blood,
tar, paste, etc.
Qn. What is
Pump? What is a turbine? / What is the difference between the turbine and the
pump?
Answer: Pump is a device which transfers mechanical energy to the fluid.
The turbine does the opposite. It transfers the flow energy of the fluid to
mechanical energy.
Qn. What are
turbo machines?
Answer: Turbomachines are devices which transfer energy to or from the
fluid by the dynamic action of rotating blades
Qn. How the
characteristics of a flow is determined?
Answer: By Reynolds Number. If Re <2300 then the flow is laminar. if
2300 <Re<4000 then the flow is transient and if Re>4000 then the flow
is turbulent.
Qn. What is the
Reynolds number?
Answer: Reynolds Number is the ratio of inertia force to viscous force.
Re = ρvL/μ
Qn. What is
Bernoulli’s equation? Why it is used?
Answer: pressure head + velocity head + datum head = constant
P1/γ + (v2 )1/2g + z1 = P2/γ +( v2)2 /2g + z1 = constant
Qn. What is the
difference between the centrifugal pump and +ve displacement pump?
Answer: In Centrifugal pump the flow rate changes with the head but in a
positive displacement pump the flow rate remains the same.
Qn. What is
cavitation in centrifugal pump? Why priming is done in centrifugal pump?
Answer: If the suction side develops a pressure less than the vapor
pressure of the water then water will start to boil and create water bubbles
and it will spoil the impeller material. It is called cavitation.
When the impeller rotates it adds a rotating motion to the adjacent
fluid and as a result, K.E and Pressure in the fluid increases and negative
pressure are developed in the suction side of the impeller. So water/fluid
flows continuously through the impeller. But when the pipe is filled with air,
the impeller rotates but the pressure difference is negligible as a result no
water flows through the pump. That’s why priming is done.
Qn. What is the
difference between the heat engine & heat pump?
Answer: Heat Engine produces work and transfers energy from high temperature
to low temperature source medium. In a Heat pump, external work is needed to
transfer energy from low to high temperature medium.
Qn. What is the
difference between an Impulse Turbine and Reaction Turbine?
Answer: In Impulse Turbine, all the pressure energy is converted to
kinetic energy but in reaction turbine, a part of the pressure energy is
converted to kinetic energy and rest remains as pressure energy.
Qn. What is
NPSH?
Answer: NPSH = Net Positive
Suction Head. It is the measure of minimum pressure which is required at the
suction pipe to keep the pump from cavitation.
Qn. What is
draft tube?
Answer: The draft tube is a conduit used in reaction turbine. The main
feature of the draft tube is, it has a shape of increasing area at the end like
a diffuser. You have know the classification and uses of draft tube if you are
working in a hydraulic power plant.
Best of luck.
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