Pneumatics and Hydraulics MCQs 2026

Flow control valve regulates

1. A only pressure unlimited rise ✓
2. B only fluid colour ✓
3. C actuator speed by restricting flow ✓
4. D only tank level without flow ✓

Pressure reducing valve maintains

1. A higher pressure upstream of pump always ✓
2. B lower constant downstream pressure ✓
3. C zero flow always ✓
4. D only vacuum 0 absolute ✓

Counterbalance valve prevents

1. A runaway descent of overrunning load on cylinder ✓
2. B only upward extension always ✓
3. C only filtration clog ✓
4. D only pump cavitation suction ✓

Sequence valve causes

1. A one branch to act after pressure threshold reached ✓
2. B simultaneous motion always without order ✓
3. C only temperature sequencing ✓
4. D only electrical phase rotation ✓

Unloading valve dumps pump to tank at

1. A maximum pressure always ✓
2. B low pressure when actuator idle saving power ✓
3. C only when filter clogged ✓
4. D only during electrical blackout without logic ✓

Hydraulic cylinder bore diameter primarily determines

1. A only speed exclusively without flow ✓
2. B only stroke length ✓
3. C force output at given pressure ✓
4. D only paint colour ✓

Cylinder rod side annular area causes

1. A equal force both directions always single rod ✓
2. B zero force retract ✓
3. C only speed difference without force difference ✓
4. D retraction force less than extension for same pressure (single rod) ✓

Double-acting cylinder has

1. A only spring return single acting always ✓
2. B only vacuum both sides ✓
3. C only one port ✓
4. D pressure on both extend and retract sides alternately ✓

Hydraulic motor converts

1. A only stores charge electrically ✓
2. B only filters oil ✓
3. C fluid power to rotary mechanical output ✓
4. D only measures pressure ✓

Cavitation in hydraulic pump is avoided by maintaining

1. A discharge at maximum blockage ✓
2. B inlet pressure above vapour pressure with adequate NPSH ✓
3. C zero oil in tank ✓
4. D only air in suction line deliberately ✓

Filtration in hydraulic system targets

1. A particle contamination to protect valves and pumps ✓
2. B only water colour ✓
3. C only nitrogen purity in bladder exclusively without oil cleanliness ✓
4. D only electrical harmonics ✓

Viscosity of hydraulic oil affects

1. A leakage, efficiency and heat generation ✓
2. B only tank paint drying time ✓
3. C only label font ✓
4. D only hose colour ✓

Fire-resistant hydraulic fluids include

1. A only pure gasoline ✓
2. B water-glycol and phosphate ester types ✓
3. C only molten sodium ✓
4. D only dry sand ✓

Air compressor types include

1. A only hydraulic gear pump ✓
2. B only steam ejector without air ✓
3. C reciprocating, screw and centrifugal ✓
4. D only jet fuel pump ✓

Aftercooler on compressor

1. A only adds water deliberately ✓
2. B only increases temperature ✓
3. C only filters oil without cooling ✓
4. D removes heat reducing moisture in air lines ✓

FRL unit in pneumatics is

1. A Fuel Rocket Launcher ✓
2. B Force Relay Logic ✓
3. C Flow Return Line ✓
4. D Filter, Regulator and Lubricator assembly ✓

Pressure regulator in pneumatic circuit maintains

1. A only maximum upstream compressor pressure without reduction ✓
2. B only vacuum ✓
3. C constant downstream pressure ✓
4. D only flow without pressure control ✓

Pneumatic cylinder speed controlled by

1. A only increasing pressure without flow restriction ✓
2. B flow control valve at exhaust or inlet ✓
3. C only larger bore always slower without flow change ✓
4. D only electrical resistance ✓

Single-acting pneumatic cylinder uses

1. A air pressure one direction and spring return ✓
2. B pressure both directions always ✓
3. C hydraulic oil always ✓
4. D only vacuum extend and pressure retract ✓

5/2 pneumatic valve for double-acting cylinder has

1. A five ports and two positions ✓
2. B three ports only ✓
3. C one port only ✓
4. D no exhaust ✓

Quick exhaust valve speeds

1. A only extend stroke always ✓
2. B cylinder return by dumping exhaust locally near cylinder ✓
3. C only compressor inlet ✓
4. D only filter drain ✓

Pneumatic logic elements (AND, OR, NOT) use

1. A only hydraulics oil 200 bar ✓
2. B only steam 100 bar ✓
3. C air signal switching without electronics ✓
4. D only vacuum tubes electronics ✓

Hydro pneumatic system combines

1. A only pure water plumbing domestic ✓
2. B only diesel engine without fluid ✓
3. C only belt conveyor ✓
4. D hydraulic power unit with pneumatic control or intensification ✓

Intensifier boosts

1. A only electrical voltage ✓
2. B only air flow CFM without pressure rise ✓
3. C only gear ratio speed only ✓
4. D hydraulic pressure using area ratio piston ✓

Open centre hydraulic system when idle

1. A blocks pump deadhead at full pressure always ✓
2. B stops pump physically ✓
3. C pump flow returns to tank through centre of DCV spool ✓
4. D only charges accumulator always ✓

Closed centre system blocks pump flow at neutral and

1. A dumps all flow always at zero pressure ✓
2. B pressure builds to compensator setting ✓
3. C only operates pneumatically ✓
4. D only uses water ✓

Thermal expansion of hydraulic oil in closed system is accommodated by

1. A rigid sealed case without relief always rupture risk ✓
2. B only ignoring temperature ✓
3. C only adding water ✓
4. D accumulator or expansion tank ✓

Bleed air from hydraulic line to remove

1. A only solid metal chips only without air concern ✓
2. B only water always ✓
3. C entrapped air causing spongy motion ✓
4. D only nitrogen only in bladder accumulator intentionally ✓

Seal leakage in hydraulic cylinder causes

1. A higher efficiency always ✓
2. B drift, inefficiency and environmental spill risk ✓
3. C automatic self-healing always ✓
4. D only faster speed beneficial ✓

Mobile hydraulics in construction equipment (Pakistan market) includes

1. A excavators, loaders and concrete pumps ✓
2. B only office HVAC exclusively ✓
3. C only domestic ceiling fans ✓
4. D only water purifier RO ✓

Pakistan industry uses pneumatics widely in

1. A textile, packaging, food processing and automotive assembly ✓
2. B only nuclear reactor core exclusively ✓
3. C only dam spillway gates without hydraulics ✓
4. D only satellite launch exclusively ✓

Water hammer in hydraulic line is mitigated by

1. A instant full close of large DCV always ✓
2. B accumulator, slow valve closure and hose flexibility ✓
3. C only removing relief valve ✓
4. D only increasing pressure above rating ✓

Differential pressure across filter indicates

1. A only oil colour darkness only without Δp ✓
2. B only tank level only ✓
3. C element clogging needing replacement ✓
4. D only ambient music ✓

Pressure gauge reads

1. A only flow rate m³/h without pressure ✓
2. B only temperature °C ✓
3. C only RPM ✓
4. D local fluid pressure in bar or psi ✓

Hydrostatic transmission combines

1. A only fixed gear ratio gearbox only ✓
2. B only belt CVT automotive only ✓
3. C only pneumatic logic ✓
4. D variable pump and motor for speed control ✓

Vacuum ejector generates vacuum using

1. A only hydraulic 300 bar oil ✓
2. B only electric resistor heat ✓
3. C Bernoulli effect from compressed air through nozzle ✓
4. D only gravity ✓

Air motor advantage in hazardous area

1. A always highest efficiency ✓
2. B no electrical spark at motor if properly exhausted ✓
3. C only works submerged in oil ✓
4. D only constant low torque ✓

Rotary actuator (rack and pinion or vane) gives

1. A limited angle oscillating motion ✓
2. B infinite continuous rotation without limits typically ✓
3. C only linear thrust ✓
4. D only vacuum ✓

Telescopic hydraulic cylinder provides

1. A long stroke with retracted short length ✓
2. B only rotation torque ✓
3. C only vacuum suction ✓
4. D only single fixed short stroke ✓

Servo valve offers

1. A only manual gate valve ✓
2. B high bandwidth precise control of actuator with feedback ✓
3. C only fixed orifice plate ✓
4. D only water tap domestic ✓

Proportional hydraulic valve provides

1. A only on-off full shift always ✓
2. B only mechanical only without electronics ✓
3. C variable spool position proportional to electrical command ✓
4. D only pneumatic 2 bar ✓

Pilot-operated valve uses

1. A only manual lever without hydraulic assist always large force ✓
2. B only spring without fluid ✓
3. C only electrical without mechanics ✓
4. D small pilot flow to shift main stage spool ✓

Check valve in hydraulic line allows

1. A bidirectional always ✓
2. B only when manually open always ✓
3. C only vacuum reverse ✓
4. D flow one direction only ✓

ISO 1219 symbol for hydraulic motor is

1. A square only compressor ✓
2. B triangle only tank ✓
3. C circle with arrow indicating rotary output ✓
4. D diamond only filter ✓

Flushing new hydraulic system removes

1. A only adds dirt deliberately ✓
2. B contamination from fabrication and assembly ✓
3. C only paints interior ✓
4. D only replaces oil with air ✓

Hydraulic hose burst is prevented by

1. A pressure relief, proper routing, shielding and inspection ✓
2. B only exceeding rating deliberately ✓
3. C only kinking sharply always ✓
4. D only using water hose ✓

Load-sensing pump adjusts

1. A displacement or swashplate to match demand flow at set margin pressure ✓
2. B only fixed maximum flow always wasting power ✓
3. C only compressed air ✓
4. D only manual hand pump ✓

4/3 direction valve has

1. A two ports only ✓
2. B nine ports only ✓
3. C no spool ✓
4. D four ports and three positions ✓

Direction control valve (DCV) functions to

1. A only measure temperature ✓
2. B only filter particles 10 micron ✓
3. C only store energy in nitrogen ✓
4. D direct fluid flow paths to extend, retract or idle actuator ✓

Relief valve in hydraulic system sets

1. A only flow direction to actuator always ✓
2. B only filtration rating micron ✓
3. C maximum system pressure by bypassing pump flow to tank ✓
4. D only tank colour ✓

Accumulator in hydraulic circuit stores

1. A only electrical charge in capacitor exclusively without fluid ✓
2. B energy as compressed gas bladder or weight on piston separating gas from oil ✓
3. C only sand ballast decorative ✓
4. D only heat in chimney ✓

Piston pump (axial or radial) suits

1. A high pressure industrial and mobile hydraulics ✓
2. B only aquarium air bubble ✓
3. C only kitchen water tap ✓
4. D only 0.1 bar pneumatic only ✓

Vane pump provides

1. A balanced design moderate pressure fixed or variable displacement ✓
2. B only vacuum without oil ✓
3. C only water hammer arrestor ✓
4. D only pneumatic only ✓

Gear pump in hydraulics is

1. A only centrifugal high flow low pressure exclusively for lift always ✓
2. B positive displacement with meshing gears ✓
3. C only steam turbine ✓
4. D only air fan ✓

Hydraulic pump converts

1. A only electrical heat to light ✓
2. B only chemical to nuclear ✓
3. C mechanical power to hydraulic energy (flow at pressure) ✓
4. D only potential to chemical ✓

Main advantage of pneumatics is

1. A highest force density always ✓
2. B zero leakage always ✓
3. C incompressible stiffest system ✓
4. D clean, fast actuation and easy exhaust at lower cost ✓

Main advantage of hydraulics over pneumatics for heavy loads is

1. A always faster exhaust without reason ✓
2. B lower force density always ✓
3. C only works above 1000°C ✓
4. D higher force in compact actuators due to high pressure ✓

Pneumatic system typically uses

1. A only water glycol oil mixture primarily ✓
2. B only molten metal ✓
3. C compressed air as working fluid ✓
4. D only hydraulic oil exclusively ✓

Hydraulic system uses

1. A only air primarily as working medium ✓
2. B incompressible fluid (oil) to transmit power ✓
3. C only steam exclusively in closed loop always ✓
4. D only vacuum without fluid ✓

Pascal's law states pressure applied to confined fluid

1. A transmits equally in all directions undiminished ✓
2. B only downward ignoring sideways ✓
3. C only to solids not fluids ✓
4. D only when fluid is compressible gas exclusively ✓