Engineering Questions with Answers - Multiple Choice Questions

# MCQs on Flow through Nozzles

1 - Question

When a gas is pushed through a pipe, the gaseous molecules are _________ by the pipe’s walls
a) Attracted
b) Absorbed
c) Deflected
d) Dissipated

c
Explanation: This is because there is no attractive force present in the tube for the process of attraction to occur. Also, the surface of pipes is not an absorbing one, hence absorption is also ruled out. A pipe is not capable of dissipation of the molecules. Hence, the right option is deflected.

2 - Question

If the speed of sound is much ________ than that of the gas, the gas density will stay constant.
a) Smaller
b) Larger
c) Equal to
d) Non-existent

b
Explanation: This is because only with speed of sound Is larger, it’ll be able to compensate for the speed of gas. Under such situations, the gas density will be able to stay constant. If they are equal, density will get compressed.

3 - Question

Isentropic nozzle flow states about the movement of a gas or fluid through a narrow orifice without an increase or decrease in ___________
a) Pressure
b) Energy
c) Displacement
d) Entropy

d
Explanation: Entropy is defined as the measure of degree of randomness. It is a thermodynamics quantity. As this nozzle flow deals with thermodynamics, entropy is the right choice. The other options are not parameters of entropy.

4 - Question

In fluid dynamics, the velocity of the fluid in the stagnation point is
a) Zero
b) Infinite
c) Non-existent
d) Negative

a
Explanation: Stagnant point is a point where there is no movement of the fluid. When there is no movement, the velocity will be 0. Hence the answer is 0.

5 - Question

The stagnation state is obtained after a _____________ to zero velocity.
a) Accelerating
b) Decelerating
c) Equilibrium
d) Exponential increase

b
Explanation: Initially the flow has a velocity. In the stagnant state, the velocity is 0. For this to happen, there should be a deceleration of the velocity. Hence, deceleration is the answer.

6 - Question

To refrain from separation in subsonic nozzles, the expansion angle must not be more than _____
a) 10 degrees
b) 20 degrees
c) 30 degrees
d) 40 degrees

a
Explanation: If the angle is more than 10 degrees, there will be a drift amidst the nozzle. At any angle more than 10 degrees, this separation will occur. But the minimum value is 10 degrees. So, the answer is 10 degrees.

7 - Question

Gas flows through the nozzle from an area of _____ pressure (called the chamber) to one of _____ pressure
a) High, low
b) Low, high
c) Same, same
d) Constant, Infinite

a
Explanation: Anything that flows or runs moves from a region of higher value to lower value. We can take the example of any physical parameter like pressure, altitude etc. Hence, here the gas will flow from high to low pressure regions.

8 - Question

Converging-diverging nozzle is also known as __________
a) Pascal nozzle
b) Bernouille’s nozzle
c) Toricelli’s nozzle
d) de Laval’ nozzle

d
Explanation: This is because this nozzle was invented by Carl de Laval. So, it is also named after him. Hence De-Laval nozzle is the option.

9 - Question

When the pressure chamber is big, the flow velocities are _________
a) Large
b) Negligible
c) Constant
d) Increasing

b
Explanation: When the chamber is large, the area is high. Velocity is inversely proportional to area. So in a large chamber, the flow velocity will be less. It will be negligible.

10 - Question

For a compressible, ideal gas, mass flow rate depends on parameters such as flow area, pressure, temperature, properties of the gas, and _________
a) Avogardo’s Number
b) Mach Number
c) Reynold’s Number
d) Le-Grange’ Number