Mechatronics Multiple Choice Questions on “Fluid Pressure Sensors”.

1. How is pressure (p) defined in terms of force(F) and area(A)?

a) p = F*A

b) p = F+A

c) p = F/A

d) p = F-A

Answer: c

Clarification: Pressure is defined as force per unit area (i.e) pressure (p) = force (F)/Area of cross-section (A). The standard unit of force and area taken is Newton and (meter)^{2}respectively.

2. What is the SI unit of pressure?

a) Pascal

b) Barye

c) Atm

d) Newton

Answer: a

Clarification: Pascal is the SI unit of pressure. 1 pascal = 1 Newton of force applied on 1 square meter of area. Barye is the CGS unit of pressure. Atm is used to measure atmospheric pressure, whereas Newton is unit of force.

3. 1 atm = ____ pascal or ______bar.

a) 101325, 101.325

b) 101325, 9.81

c) 1.01325, 101325

d) 101325, 1.01325

Answer: d

Clarification: 1 atm = 101325 Pascal or 1.01325 bar. 1 atm is the atmospheric pressure above the sea level (i.e) pressure exerted by the atmosphere above the sea level. Pascal is the SI unit of pressure and 1 atmospheric pressure is equal to 101325 Pascal.

4. Whose pressure can be determined by the bourdon tube pressure gauge?

a) Solids

b) Fluids

c) Only Gas

d) Only liquids

Answer: b

Clarification: Bourdon tube can determine the pressure of the fluids. Fluids include all the materials that can flow, be it gas or liquid. Bourdon tube is curved, hollow tube. When the pressure in the tube increases, it causes a deformation in the shape of the tube. This deformation is used to determine the amount of pressure exerted by the fluid in the tube.

5. Absolute pressure is the sum of over pressure and atmospheric pressure.

a) True

b) False

Answer: a

Clarification: Absolute pressure is the sum of over pressure and atmospheric pressure. Over pressure is commonly known as gauge pressure, therefore P(abs)={P(over) or P(gauge)}+P(atm).

6. Gauge pressure is the summation of absolute pressure and atmospheric pressure.

a) True

b) False

Answer: b

Clarification: Gauge pressure is the not summation of absolute pressure and atmospheric pressure. It the difference between the absolute pressure and atmospheric pressure (i.e)P(gauge)=P(abs)-P(atm).

7. Which is not equal to 1 atmospheric pressure?

a) 101325 Pascal

b) 1.01325 Bar

c) 101.325 torr

d) 760 torr

Answer: c

Clarification: 101.325 torr is not equal to 1 atmospheric pressure. 1 atmospheric pressure is equal to 101325 pascal or 1.01325 bar or 760 torr. Pascal is the SI unit of pressure.

8. Which fluid is commonly used in U-tube manometers as a reference, in determining the pressure of the liquid?

a) Sodium

b) Argon

c) Water

d) Mercury

Answer: d

Clarification: Mercury is commonly used fluid in U-tube manometers as a reference, in determining the pressure of the liquid. The specific gravity of mercury is 13.6 which mean that it is 13.6 times heavier than water.

9. What is the pressure experienced by a wall, if a brick is thrown with a force 10 Newton and cross-section area of contact is 2 square metres?

a) 5 Pascal

b) 5 Atm

c) 5 barye

d) 1 Atm

Answer: a

Clarification: Given:

Force of brick thrown=10 Newton

Cross-section area=2m^{2}

Since pressure (p)=Force of brick thrown (F)/Area of cross-section (A),

P=10N/2m^{2}=5 pascal.

10. Which is an example of pressure sensor?

a) MSP430G2ET

b) CMCP793V-500

c) SLB700A/06VA

d) BMP180

Answer: d

Clarification: BMP180 is an example of pressure sensor. SLB700A/06VA is an example of force sensor. MSP430G2ET is a development board manufactured by the “TEXAS INSTRUMENTS” and CMCP793V-500 is a velocity sensor.

11. What is the pressure experienced by a pressure sensor, if a rigid body is thrown normally with a force 5 Newton and cross-section area of contact is 1 square metre?

a) 5 Pascal

b) 5 Atm

c) 5 Barye

d) 1 Atm

Answer: a

Clarification: Given;

Force of brick thrown=5 Newton

Cross-section area=1 m^{2}

Since pressure (p) = Force of brick thrown (F)/Area of cross-section (A),

P=5N/1m^{2}=5 Pascal.

12. What is the absolute pressure experienced by a pressure sensor, if the atmospheric pressure of a fluid is 2 atm, gauge pressure is 5 atm and differential pressure is 3 atm?

a) 5 pascal

b) 5 Atm

c) 7 barye

d) 7 Atm

Answer: d

Clarification: Given;

Atmospheric pressure=2 atm

Gauge pressure=5atm

Differential pressure=3 atm

Absolute pressure=Gauge pressure+Atmospheric pressure

Absolute pressure=5atm+2atm => 7atm

13. What is the gauge pressure experienced by a pressure sensor, if the atmospheric pressure of a fluid is 1 atm, absolute pressure is 6 atm and differential pressure is 2 atm?

a) 5 pascal

b) 5 Atm

c) 5 barye

d) 1 Atm

Answer: b

Clarification: Given;

Atmospheric pressure = 1 atm

Absolute pressure = 6 atm

Differential pressure = 3 atm

Gauge pressure = Absolute pressure-Atmospheric pressure

Gauge pressure = 6 atm-1atm => 5atm

14. What is the cross-section area of contact, if a brick is thrown with a force 10 Newton and the pressure experienced by a wall is 5 Pascal?

a) 2m^{2}

b) 5m^{2}

c) 4m^{2}

d) 3m^{2}

Answer: a

Clarification: Given:

Force of brick thrown=10 Newton

Pressure experienced by a wall=5 Pascal

Since pressure (p)=Force of brick thrown (F)/Area of cross-section (A),

5 Pascal=10/A

Area of cross-section (A)=2m^{2}

15. What is the pressure experienced by a pressure sensor, if a rigid body is thrown normally with a force 6 Newton and cross-section area of contact is 2 square metres?

a) 3 Pascal

b) 3 Atm

c) 3 Barye

d) 12 Atm

Answer: a

Clarification: Given:

Force of brick thrown=6 Newton

Cross-section area=2m^{2}

Since pressure (p)=Force of brick thrown (F)/Area of cross-section (A),

P=6N/2m^{2}=3 Pascal.

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