# Mechatronics Questions and Answers – Pneumatic and Hydraulic Circuits

This set of Mechatronics Multiple Choice Questions & Answers (MCQs) focuses on “Pneumatic and Hydraulic Circuits”.

1. In which type of system does power transmission takes place through compressed air?
a) Fluid power system
b) Hydraulic system
c) Pneumatic system
d) Stepper motors

Explanation: Pneumatic system is a power transmission system in which, the transmission of power takes place through compressed air. The mechanical energy is given to compressor, that is, the shaft of the compressor is rotated by any means of the prime mover. The fluid Power system is a power transmission system in which, the transmission of power takes place by means of “oil under pressure” or “compressed air”. If “oil under pressure” is used in the system for power transmission then the system is called a hydraulic system.

2. The compressed air flows to the actuator through ____
a) Pipes and valves
b) Shafts
c) Motors
d) Flow control valve

Explanation: Compressor drives air from the atmosphere and the compressed air flow through actuator through pipes and valves. Actuator produces back the mechanical energy that can either be the linear motion of cylinder or rotary motion of the air motor shaft. The other sources mentioned in the options are not the sources for the flow of compressed air.

3. The compressed air is delivered to the pneumatic system through the air compressor.
a) True
b) False

Explanation: The air compressor draws the air from the atmosphere, compresses it and delivers the compressed air to the pneumatic system. Compressor drives air from the atmosphere and the compressed air flow through actuator through pipes and valves.

4. What is the function of the air dryer?
a) Removes dirt
b) Removes moisture
c) Controls the rate of flow
d) Controls the pressure

Explanation: The compressed air delivered by the compressor contains moisture from the atmosphere. This moisture is separated and removed by the air dryer. Only the dry compressed air is given to the pneumatic system.

5. Which part of the Pneumatic system stores the compressed air?
a) Air dryer
b) Air compressor
d) Air lubricator

Explanation: The air receiver tank stores the compressed air. Apart from storing the compressed air, it has several other functions also. It acts as cooler to cool the hot compressed air. It acts as moisture separator to separate and remove the water.
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6. Which type of pumps can give discharge even at high pressure?
a) Multistage Pumps
b) Monoblock pumps
c) Rotary pumps
d) Single stage pumps

Explanation: Rotary pumps are positive displacement pumps. Rotary pumps have two or more rotating components. The discharge of rotary components remains almost the same irrespective of pressure. They can give discharge even at high pressure. In the other options, the type of pumps mentioned is all non-positive displacement types.

7. Which type of component in the hydraulic system supports less vibration and noise?
a) Flow control valve
b) Oil reservoir
c) Rotatory pumps
d) Pressure gauge

Explanation: Very less vibration and noise are observed in the case of rotary pumps. These pumps are compact with very a smaller number of moving components. The flow control valves, oil reservoir and pressure gauge are the other parts of the hydraulic system with different functions.

8. Hydraulic systems are slower in operation.
a) True
b) False

Explanation: As oil has more viscosity, it cannot flow fast. Hence Hydraulic systems are slower in operation. Hydraulic oils are petroleum based oils, they are inflammable and there is every chance of fire hazard if this is neglected.

9. What prevents the leakage of oil inside an unbalanced vane pump?
a) Vanes
b) Cylindrical rotor
c) Screw
d) Difference between the pressure of inlet and outlet

Explanation: The vanes are seated in the radial slots of the rotor and held against the casing by spring force or hydraulic force. Hence there will not be any leakage of oil between the vane tips and the casing. Still, there is a little amount of leakage and hence the volumetric efficiency will be around 95%.

10. Which among the following are not the main selection criteria for selection of hydraulic pumps?
a) Discharge
b) Pressure
c) Speed
d) Weight

Explanation: The weight is not the main selection criteria for selection of hydraulic pumps. There are different values for gear pumps, vane pumps and piston pumps for Pressure, Discharge and Speed which are predefined values.

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