Pneumatics and Hydraulics MCQs 2026

Mobile hydraulics in construction equipment (Pakistan market) includes

1. Aexcavators, loaders and concrete pumps✓
2. Bonly office HVAC exclusively✓
3. Conly domestic ceiling fans✓
4. Donly water purifier RO✓

Pascal's law states pressure applied to confined fluid

1. Atransmits equally in all directions undiminished✓
2. Bonly downward ignoring sideways✓
3. Conly to solids not fluids✓
4. Donly when fluid is compressible gas exclusively✓

Hydraulic system uses

1. Aonly air primarily as working medium✓
2. Bincompressible fluid (oil) to transmit power✓
3. Conly steam exclusively in closed loop always✓
4. Donly vacuum without fluid✓

Pneumatic system typically uses

1. Aonly water glycol oil mixture primarily✓
2. Bonly molten metal✓
3. Ccompressed air as working fluid✓
4. Donly hydraulic oil exclusively✓

Main advantage of hydraulics over pneumatics for heavy loads is

1. Aalways faster exhaust without reason✓
2. Blower force density always✓
3. Conly works above 1000°C✓
4. Dhigher force in compact actuators due to high pressure✓

Main advantage of pneumatics is

1. Ahighest force density always✓
2. Bzero leakage always✓
3. Cincompressible stiffest system✓
4. Dclean, fast actuation and easy exhaust at lower cost✓

Hydraulic pump converts

1. Aonly electrical heat to light✓
2. Bonly chemical to nuclear✓
3. Cmechanical power to hydraulic energy (flow at pressure)✓
4. Donly potential to chemical✓

Gear pump in hydraulics is

1. Aonly centrifugal high flow low pressure exclusively for lift always✓
2. Bpositive displacement with meshing gears✓
3. Conly steam turbine✓
4. Donly air fan✓

Vane pump provides

1. Abalanced design moderate pressure fixed or variable displacement✓
2. Bonly vacuum without oil✓
3. Conly water hammer arrestor✓
4. Donly pneumatic only✓

Piston pump (axial or radial) suits

1. Ahigh pressure industrial and mobile hydraulics✓
2. Bonly aquarium air bubble✓
3. Conly kitchen water tap✓
4. Donly 0.1 bar pneumatic only✓

Accumulator in hydraulic circuit stores

1. Aonly electrical charge in capacitor exclusively without fluid✓
2. Benergy as compressed gas bladder or weight on piston separating gas from oil✓
3. Conly sand ballast decorative✓
4. Donly heat in chimney✓

Relief valve in hydraulic system sets

1. Aonly flow direction to actuator always✓
2. Bonly filtration rating micron✓
3. Cmaximum system pressure by bypassing pump flow to tank✓
4. Donly tank colour✓

Direction control valve (DCV) functions to

1. Aonly measure temperature✓
2. Bonly filter particles 10 micron✓
3. Conly store energy in nitrogen✓
4. Ddirect fluid flow paths to extend, retract or idle actuator✓

4/3 direction valve has

1. Atwo ports only✓
2. Bnine ports only✓
3. Cno spool✓
4. Dfour ports and three positions✓

Load-sensing pump adjusts

1. Adisplacement or swashplate to match demand flow at set margin pressure✓
2. Bonly fixed maximum flow always wasting power✓
3. Conly compressed air✓
4. Donly manual hand pump✓

Hydraulic hose burst is prevented by

1. Apressure relief, proper routing, shielding and inspection✓
2. Bonly exceeding rating deliberately✓
3. Conly kinking sharply always✓
4. Donly using water hose✓

Flushing new hydraulic system removes

1. Aonly adds dirt deliberately✓
2. Bcontamination from fabrication and assembly✓
3. Conly paints interior✓
4. Donly replaces oil with air✓

ISO 1219 symbol for hydraulic motor is

1. Asquare only compressor✓
2. Btriangle only tank✓
3. Ccircle with arrow indicating rotary output✓
4. Ddiamond only filter✓

Check valve in hydraulic line allows

1. Abidirectional always✓
2. Bonly when manually open always✓
3. Conly vacuum reverse✓
4. Dflow one direction only✓

Pilot-operated valve uses

1. Aonly manual lever without hydraulic assist always large force✓
2. Bonly spring without fluid✓
3. Conly electrical without mechanics✓
4. Dsmall pilot flow to shift main stage spool✓

Proportional hydraulic valve provides

1. Aonly on-off full shift always✓
2. Bonly mechanical only without electronics✓
3. Cvariable spool position proportional to electrical command✓
4. Donly pneumatic 2 bar✓

Servo valve offers

1. Aonly manual gate valve✓
2. Bhigh bandwidth precise control of actuator with feedback✓
3. Conly fixed orifice plate✓
4. Donly water tap domestic✓

Telescopic hydraulic cylinder provides

1. Along stroke with retracted short length✓
2. Bonly rotation torque✓
3. Conly vacuum suction✓
4. Donly single fixed short stroke✓

Rotary actuator (rack and pinion or vane) gives

1. Alimited angle oscillating motion✓
2. Binfinite continuous rotation without limits typically✓
3. Conly linear thrust✓
4. Donly vacuum✓

Air motor advantage in hazardous area

1. Aalways highest efficiency✓
2. Bno electrical spark at motor if properly exhausted✓
3. Conly works submerged in oil✓
4. Donly constant low torque✓

Vacuum ejector generates vacuum using

1. Aonly hydraulic 300 bar oil✓
2. Bonly electric resistor heat✓
3. CBernoulli effect from compressed air through nozzle✓
4. Donly gravity✓

Hydrostatic transmission combines

1. Aonly fixed gear ratio gearbox only✓
2. Bonly belt CVT automotive only✓
3. Conly pneumatic logic✓
4. Dvariable pump and motor for speed control✓

Pressure gauge reads

1. Aonly flow rate m³/h without pressure✓
2. Bonly temperature °C✓
3. Conly RPM✓
4. Dlocal fluid pressure in bar or psi✓

Differential pressure across filter indicates

1. Aonly oil colour darkness only without Δp✓
2. Bonly tank level only✓
3. Celement clogging needing replacement✓
4. Donly ambient music✓

Water hammer in hydraulic line is mitigated by

1. Ainstant full close of large DCV always✓
2. Baccumulator, slow valve closure and hose flexibility✓
3. Conly removing relief valve✓
4. Donly increasing pressure above rating✓

Pakistan industry uses pneumatics widely in

1. Atextile, packaging, food processing and automotive assembly✓
2. Bonly nuclear reactor core exclusively✓
3. Conly dam spillway gates without hydraulics✓
4. Donly satellite launch exclusively✓

Seal leakage in hydraulic cylinder causes

1. Ahigher efficiency always✓
2. Bdrift, inefficiency and environmental spill risk✓
3. Cautomatic self-healing always✓
4. Donly faster speed beneficial✓

Bleed air from hydraulic line to remove

1. Aonly solid metal chips only without air concern✓
2. Bonly water always✓
3. Centrapped air causing spongy motion✓
4. Donly nitrogen only in bladder accumulator intentionally✓

Thermal expansion of hydraulic oil in closed system is accommodated by

1. Arigid sealed case without relief always rupture risk✓
2. Bonly ignoring temperature✓
3. Conly adding water✓
4. Daccumulator or expansion tank✓

Flow control valve regulates

1. Aonly pressure unlimited rise✓
2. Bonly fluid colour✓
3. Cactuator speed by restricting flow✓
4. Donly tank level without flow✓

Hydro pneumatic system combines

1. Aonly pure water plumbing domestic✓
2. Bonly diesel engine without fluid✓
3. Conly belt conveyor✓
4. Dhydraulic power unit with pneumatic control or intensification✓

Closed centre system blocks pump flow at neutral and

1. Adumps all flow always at zero pressure✓
2. Bpressure builds to compensator setting✓
3. Conly operates pneumatically✓
4. Donly uses water✓

Open centre hydraulic system when idle

1. Ablocks pump deadhead at full pressure always✓
2. Bstops pump physically✓
3. Cpump flow returns to tank through centre of DCV spool✓
4. Donly charges accumulator always✓

Intensifier boosts

1. Aonly electrical voltage✓
2. Bonly air flow CFM without pressure rise✓
3. Conly gear ratio speed only✓
4. Dhydraulic pressure using area ratio piston✓

Pneumatic logic elements (AND, OR, NOT) use

1. Aonly hydraulics oil 200 bar✓
2. Bonly steam 100 bar✓
3. Cair signal switching without electronics✓
4. Donly vacuum tubes electronics✓

Quick exhaust valve speeds

1. Aonly extend stroke always✓
2. Bcylinder return by dumping exhaust locally near cylinder✓
3. Conly compressor inlet✓
4. Donly filter drain✓

5/2 pneumatic valve for double-acting cylinder has

1. Afive ports and two positions✓
2. Bthree ports only✓
3. Cone port only✓
4. Dno exhaust✓

Single-acting pneumatic cylinder uses

1. Aair pressure one direction and spring return✓
2. Bpressure both directions always✓
3. Chydraulic oil always✓
4. Donly vacuum extend and pressure retract✓

Pneumatic cylinder speed controlled by

1. Aonly increasing pressure without flow restriction✓
2. Bflow control valve at exhaust or inlet✓
3. Conly larger bore always slower without flow change✓
4. Donly electrical resistance✓

Pressure regulator in pneumatic circuit maintains

1. Aonly maximum upstream compressor pressure without reduction✓
2. Bonly vacuum✓
3. Cconstant downstream pressure✓
4. Donly flow without pressure control✓

FRL unit in pneumatics is

1. AFuel Rocket Launcher✓
2. BForce Relay Logic✓
3. CFlow Return Line✓
4. DFilter, Regulator and Lubricator assembly✓

Viscosity of hydraulic oil affects

1. Aleakage, efficiency and heat generation✓
2. Bonly tank paint drying time✓
3. Conly label font✓
4. Donly hose colour✓

Aftercooler on compressor

1. Aonly adds water deliberately✓
2. Bonly increases temperature✓
3. Conly filters oil without cooling✓
4. Dremoves heat reducing moisture in air lines✓

Pressure reducing valve maintains

1. Ahigher pressure upstream of pump always✓
2. Blower constant downstream pressure✓
3. Czero flow always✓
4. Donly vacuum 0 absolute✓

Counterbalance valve prevents

1. Arunaway descent of overrunning load on cylinder✓
2. Bonly upward extension always✓
3. Conly filtration clog✓
4. Donly pump cavitation suction✓

Sequence valve causes

1. Aone branch to act after pressure threshold reached✓
2. Bsimultaneous motion always without order✓
3. Conly temperature sequencing✓
4. Donly electrical phase rotation✓

Unloading valve dumps pump to tank at

1. Amaximum pressure always✓
2. Blow pressure when actuator idle saving power✓
3. Conly when filter clogged✓
4. Donly during electrical blackout without logic✓

Hydraulic cylinder bore diameter primarily determines

1. Aonly speed exclusively without flow✓
2. Bonly stroke length✓
3. Cforce output at given pressure✓
4. Donly paint colour✓

Cylinder rod side annular area causes

1. Aequal force both directions always single rod✓
2. Bzero force retract✓
3. Conly speed difference without force difference✓
4. Dretraction force less than extension for same pressure (single rod)✓

Double-acting cylinder has

1. Aonly spring return single acting always✓
2. Bonly vacuum both sides✓
3. Conly one port✓
4. Dpressure on both extend and retract sides alternately✓

Hydraulic motor converts

1. Aonly stores charge electrically✓
2. Bonly filters oil✓
3. Cfluid power to rotary mechanical output✓
4. Donly measures pressure✓

Cavitation in hydraulic pump is avoided by maintaining

1. Adischarge at maximum blockage✓
2. Binlet pressure above vapour pressure with adequate NPSH✓
3. Czero oil in tank✓
4. Donly air in suction line deliberately✓

Filtration in hydraulic system targets

1. Aparticle contamination to protect valves and pumps✓
2. Bonly water colour✓
3. Conly nitrogen purity in bladder exclusively without oil cleanliness✓
4. Donly electrical harmonics✓

Air compressor types include

1. Aonly hydraulic gear pump✓
2. Bonly steam ejector without air✓
3. Creciprocating, screw and centrifugal✓
4. Donly jet fuel pump✓

Fire-resistant hydraulic fluids include

1. Aonly pure gasoline✓
2. Bwater-glycol and phosphate ester types✓
3. Conly molten sodium✓
4. Donly dry sand✓