I85PREP
⌘ K
IFPS CFPS study materials
IFPS CFPS study resources

IFPS CFPS practice questions

One question at a time. Build your IFPS CFPS understanding.

First 50 of 200 questions. Each one lists the choices, the correct answer, and an explanation. The checker at the top of this page saves progress in this browser when it is available.

Continue in the practice tool above to load more questions, 50 at a time.

Question 1Fluid Power Fundamentals

In a hydraulic circuit, which quantity is defined as the force per unit area acting perpendicular to a surface?

  1. Pressure Correct answer.
  2. Viscosity
  3. Flow rate
  4. Bulk modulus

Explanation

Pressure is defined as normal force divided by the area over which it acts, expressed in pascals (N/m²) or bar. Flow rate measures volume passing per unit time, viscosity resists shear, and bulk modulus measures compressibility. Only pressure has the force-per-area definition.

Question 2Fluid Power Fundamentals

What is the approximate gauge pressure at the bottom of a 10 m column of hydraulic oil with a density of 900 kg/m³, using g = 9.81 m/s²?

  1. 883 kPa
  2. 88.3 kPa Correct answer.
  3. 0.883 kPa
  4. 8.83 kPa

Explanation

Hydrostatic pressure equals density times gravity times height: 900 × 9.81 × 10 ≈ 88,290 Pa, or about 88.3 kPa. This is the standard hydrostatic relationship used for reservoir and column calculations. The other values differ by factors of ten.

Question 3Fluid Power Fundamentals

According to Pascal's law, an enclosed static fluid transmits an applied pressure change in which manner?

  1. Only in the direction of the applied force
  2. Only to surfaces perpendicular to gravity
  3. Reduced in proportion to depth below the piston
  4. Equally to every point of the confined fluid Correct answer.

Explanation

Pascal's law states that a pressure change applied to a confined fluid is transmitted undiminished to all points of the fluid and to the walls of the container. This principle underlies hydraulic press and intensifier design. Directional or depth-dependent reduction contradicts the law.

Question 4Fluid Power Fundamentals

A hydraulic cylinder with a piston area of 0.005 m² must produce 20 kN of extending force. What pressure is required?

  1. 40 MPa
  2. 400 kPa
  3. 0.4 MPa
  4. 4 MPa Correct answer.

Explanation

Pressure equals force divided by area: 20,000 N ÷ 0.005 m² = 4,000,000 Pa, which is 4 MPa. This is the fundamental actuator sizing relationship. The distractors reflect decimal-place errors in the division.

Question 5Fluid Power Fundamentals

In a hydraulic system, what does the term 'flow rate' describe?

  1. The volume of fluid passing a point per unit time Correct answer.
  2. The resistance of the fluid to shear
  3. The pressure drop across a filter
  4. The force exerted on the fluid by the pump

Explanation

Flow rate is the volume of fluid crossing a given section per unit time, commonly expressed in litres per minute. It governs actuator speed when divided by effective area. Force, shear resistance, and pressure drop are separate concepts.

Question 6Fluid Power Fundamentals

Oil flows through a 20 mm internal diameter pipe at 1.2 m/s. What is the approximate flow rate in litres per minute?

  1. 2.26 L/min
  2. 22.6 L/min Correct answer.
  3. 226 L/min
  4. 0.226 L/min

Explanation

Cross-sectional area is π × (0.01 m)² ≈ 3.1416 × 10⁻⁴ m². Multiplying by 1.2 m/s gives about 3.77 × 10⁻⁴ m³/s, which is 0.377 L/s or roughly 22.6 L/min. Converting cubic metres per second to litres per minute by multiplying by 60,000 completes the calculation.

Question 7Fluid Power Fundamentals

For steady incompressible flow through a pipe that narrows, the continuity equation predicts which behaviour at the smaller section?

  1. Lower velocity and higher pressure
  2. Higher velocity and lower pressure Correct answer.
  3. Unchanged velocity and unchanged pressure
  4. Higher velocity and higher pressure

Explanation

Continuity requires the area-velocity product to stay constant, so a smaller area forces a higher velocity. Bernoulli's equation then shows that where velocity rises, static pressure falls in the absence of losses. The combination of higher velocity with higher pressure violates energy conservation.

Question 8Fluid Power Fundamentals

Which statement correctly describes the relationship between absolute pressure and gauge pressure?

  1. Absolute pressure equals gauge pressure plus atmospheric pressure Correct answer.
  2. Absolute pressure is always negative in hydraulic systems
  3. Gauge pressure is always measured relative to vacuum
  4. Absolute pressure equals gauge pressure minus atmospheric pressure

Explanation

Gauge pressure uses local atmospheric pressure as its zero reference, so absolute pressure is gauge pressure plus atmospheric pressure. Vacuum gauges read negative gauge values relative to atmosphere. Absolute pressure cannot be negative, since it is referenced to a perfect vacuum.

Question 9Fluid Power Fundamentals

A fluid has a dynamic viscosity of 0.05 Pa·s and a density of 850 kg/m³. What is its kinematic viscosity?

  1. 1.18 × 10⁻⁴ m²/s
  2. 5.88 × 10⁻² m²/s
  3. 5.88 × 10⁻⁵ m²/s Correct answer.
  4. 4.25 × 10⁻² m²/s

Explanation

Kinematic viscosity equals dynamic viscosity divided by density: 0.05 ÷ 850 ≈ 5.88 × 10⁻⁵ m²/s. This quantity appears in Reynolds number calculations. Multiplying instead of dividing, or misplacing the decimal, produces the other values.

Question 10Fluid Power Fundamentals

Which fluid property most directly indicates resistance to compression and is used to model entrained air effects in hydraulic oil?

  1. Specific gravity
  2. Vapour pressure
  3. Bulk modulus Correct answer.
  4. Surface tension

Explanation

The bulk modulus expresses how much pressure is needed to produce a given fractional volume change, so it governs stiffness and compressibility. Entrained air sharply lowers effective bulk modulus. Specific gravity, surface tension, and vapour pressure describe other, unrelated behaviours.

Question 11Fluid Power Fundamentals

What is the primary physical cause of cavitation in a hydraulic pump inlet?

  1. Air leaking into the reservoir breather
  2. Local pressure falling below the fluid's vapour pressure Correct answer.
  3. Excessive back pressure in the return line
  4. Excessive fluid viscosity at high temperature

Explanation

Cavitation occurs when local static pressure drops below vapour pressure, causing vapour bubbles that collapse downstream. Restricted inlets, high speed, and cold oil raise the risk. Viscosity, breather leakage, and return pressure may contribute to aeration or heating but are not the defining mechanism.

Question 12Fluid Power Fundamentals

Which expression gives the Reynolds number for flow in a circular pipe?

  1. Re = ρvD/μ Correct answer.
  2. Re = ρv/μD
  3. Re = μvD/ρ
  4. Re = ρD/μv

Explanation

Reynolds number is inertial force divided by viscous force, which for a pipe reduces to density times velocity times diameter divided by dynamic viscosity. It may equivalently be written as velocity times diameter divided by kinematic viscosity. The other arrangements invert or omit terms.

Question 13Fluid Power Fundamentals

Oil with kinematic viscosity 4 × 10⁻⁵ m²/s flows at 1.5 m/s through a 30 mm bore hose. What is the Reynolds number, and what flow regime does it indicate?

  1. About 113, transitional
  2. About 11,250, turbulent
  3. About 1125, turbulent
  4. About 1125, laminar Correct answer.

Explanation

Re = vD/ν = (1.5 × 0.03) ÷ (4 × 10⁻⁵) = 0.045 ÷ 0.00004 ≈ 1125. Values well below roughly 2000 indicate laminar flow in pipes. The other options misplace a decimal or misapply the regime threshold.

Question 14Fluid Power Fundamentals

In a hydraulic circuit, what does Bernoulli's equation express for steady, incompressible, frictionless flow along a streamline?

  1. Conservation of momentum across a bend
  2. Conservation of energy per unit weight of fluid Correct answer.
  3. Conservation of mass between two sections
  4. Conservation of heat in the fluid

Explanation

Bernoulli's equation sums pressure head, velocity head, and elevation head as constant along a streamline, expressing energy conservation per unit weight. Mass conservation is the continuity equation, and momentum conservation is treated separately. Heat conservation is not part of the ideal-flow relation.

Question 15Fluid Power Fundamentals

A hydraulic motor receives 40 L/min and discharges 36 L/min at a pressure drop of 150 bar. What is the approximate volumetric efficiency?

  1. 80%
  2. 10%
  3. 111%
  4. 90% Correct answer.

Explanation

Volumetric efficiency is delivered flow divided by inlet flow: 36 ÷ 40 = 0.90, or 90 percent. The shortfall represents internal leakage. The other figures invert the ratio or use an unrelated comparison.

Question 16Fluid Power Fundamentals

Why is hydraulic fluid typically considered nearly incompressible in system modelling?

  1. Its density is very low compared with gases
  2. Its viscosity is independent of pressure
  3. Its bulk modulus is very high compared with gases Correct answer.
  4. Its vapour pressure is close to atmospheric

Explanation

A high bulk modulus means a large pressure change produces only a small fractional volume change, so the fluid behaves stiffly. Low density, constant viscosity, and vapour pressure are separate properties and do not explain incompressibility. Entrained air can significantly reduce the effective bulk modulus.

Question 17Fluid Power Fundamentals

Which statement best describes laminar flow in a hydraulic conduit?

  1. Pressure gradient is independent of viscosity
  2. Fluid particles move randomly with strong cross-stream mixing
  3. Velocity is uniform across the entire cross-section
  4. Fluid particles move in orderly parallel layers with little mixing Correct answer.

Explanation

Laminar flow features smooth, layered motion in which viscous forces dominate and mixing between layers is minimal. The parabolic velocity profile means velocity is not uniform across the section. Random mixing and flat profiles characterise turbulent flow instead.

Question 18Fluid Power Fundamentals

In a hydraulic system, what is the function of a pressure relief valve?

  1. To limit maximum system pressure by diverting flow to tank Correct answer.
  2. To remove particulate contamination from the fluid
  3. To regulate actuator speed by throttling flow
  4. To prevent reverse flow when the pump stops

Explanation

A relief valve opens when pressure reaches its setting and bypasses flow to the reservoir, protecting components from overpressure. Speed control by throttling is the role of flow control valves, reverse-flow protection belongs to check valves, and contamination control to filters.

Question 19Fluid Power Fundamentals

A hydraulic cylinder extends 200 mm in 5 seconds. What is the average extension speed?

  1. 0.04 m/s Correct answer.
  2. 0.4 m/s
  3. 0.004 m/s
  4. 4 m/s

Explanation

Speed equals distance divided by time: 0.2 m ÷ 5 s = 0.04 m/s, equivalent to 40 mm/s. This relationship links flow rate, bore area, and cycle time in actuator sizing. The other values reflect decimal errors.

Question 20Fluid Power Fundamentals

A double-acting cylinder has a bore of 80 mm and a rod diameter of 40 mm. What is the approximate annulus area used during retraction?

  1. 3770 mm² Correct answer.
  2. 5030 mm²
  3. 2520 mm²
  4. 1260 mm²

Explanation

Bore area is π/4 × 80² ≈ 5027 mm² and rod area is π/4 × 40² ≈ 1257 mm². The annulus area is the difference, about 3770 mm². Retraction force and retraction speed must be calculated from this reduced area, not the full bore area.

Question 21Fluid Power Fundamentals

Which factor most strongly raises the pressure drop across a hydraulic filter at constant flow?

  1. Accumulation of captured contaminants in the element Correct answer.
  2. Reducing the fluid's temperature
  3. Raising the fluid's bulk modulus
  4. Increasing the filter's flow capacity

Explanation

As contaminants accumulate, the effective open area of the element decreases and resistance rises, so differential pressure climbs at constant flow. Higher flow capacity would lower the drop, bulk modulus does not govern restriction, and reducing temperature usually increases viscosity and pressure drop as a secondary effect rather than the primary cause.

Question 22Fluid Power Fundamentals

In a closed hydraulic circuit, what is the main purpose of the charge pump?

  1. To filter the return flow before it reaches the reservoir
  2. To replenish leakage and maintain low-side pressure Correct answer.
  3. To cool the fluid by circulating it through a cooler
  4. To supply high-pressure flow to the actuator

Explanation

A charge pump makes up internal leakage in a closed loop and maintains sufficient low-side pressure to prevent cavitation and support control response. High-pressure actuator flow comes from the main pump, while cooling and filtration are handled by separate circuits or components.

Question 23Fluid Power Fundamentals

A pump delivers 60 L/min at 200 bar. Neglecting losses, what hydraulic power is transmitted to the fluid?

  1. 120 kW
  2. 2 kW
  3. 20 kW Correct answer.
  4. 12 kW

Explanation

Hydraulic power equals pressure times flow: 200 bar × 60 L/min, converted to SI gives 20 × 10⁶ Pa × 0.001 m³/s = 20,000 W, or 20 kW. A convenient check is kW ≈ bar × L/min ÷ 600. The other values reflect conversion errors.

Question 24Fluid Power Fundamentals

What distinguishes a hydrostatic transmission from a hydrodynamic one?

  1. Hydrostatic uses only fixed-displacement components
  2. Hydrostatic operates only with compressible gases
  3. Hydrostatic uses positive-displacement pumps and motors with confined fluid Correct answer.
  4. Hydrostatic relies on kinetic energy transfer in a torque converter

Explanation

Hydrostatic transmissions transfer energy through pressurised, confined fluid using positive-displacement pumps and motors, allowing high torque at low speed. Hydrodynamic drives rely on kinetic energy exchange between impeller and runner. Hydrostatic units may be variable displacement, and they use liquid, not gas.

Question 25Fluid Power Fundamentals

Which statement about the velocity profile of fully developed laminar flow in a circular pipe is correct?

  1. Velocity is uniform across the section
  2. Velocity is maximum at the wall and zero at the centreline
  3. Velocity is zero at both wall and centreline
  4. Velocity is maximum at the centreline and zero at the wall Correct answer.

Explanation

Viscous action at the wall brings velocity to zero there, and the profile is parabolic with its peak at the centreline. For laminar pipe flow the mean velocity is half the centreline value. Uniform profiles and zero centreline velocity contradict this behaviour.

Question 26Fluid Power Fundamentals

In a hydraulic circuit, which component converts fluid pressure and flow into linear mechanical force and motion?

  1. Hydraulic filter
  2. Accumulator
  3. Hydraulic cylinder Correct answer.
  4. Pressure relief valve

Explanation

A hydraulic cylinder is the actuator that receives pressurized fluid and produces linear force and displacement through its piston and rod. It is the standard linear actuator in fluid power systems, whereas accumulators store energy, relief valves limit pressure, and filters remove contaminants.

Question 27Fluid Power Fundamentals

Which statement best defines the term 'flow rate' in a hydraulic system?

  1. The pressure exerted by the fluid on the conductor walls
  2. The force required to move the fluid through a valve
  3. The volume of fluid passing a cross-section per unit time Correct answer.
  4. The speed at which the fluid moves through a conductor

Explanation

Flow rate is defined as volume per unit time, commonly expressed in litres per minute or gallons per minute. It is distinct from fluid velocity, which is distance per unit time, and from pressure, which is force per unit area.

Question 28Fluid Power Fundamentals

What is the standard SI unit of pressure used in hydraulic calculations?

  1. Newton
  2. Joule
  3. Watt
  4. Pascal Correct answer.

Explanation

The pascal (Pa) is the SI derived unit of pressure, equal to one newton per square metre. Hydraulic pressures are often expressed in bar or megapascals, but the coherent SI unit is the pascal.

Question 29Fluid Power Fundamentals

Which fluid property is defined as resistance to shear when the fluid is in motion?

  1. Viscosity Correct answer.
  2. Specific gravity
  3. Bulk modulus
  4. Density

Explanation

Viscosity is the measure of a fluid's internal resistance to shear flow. It arises from cohesion and momentum transfer between fluid layers moving at different velocities.

Question 30Fluid Power Fundamentals

A hydraulic pump has a theoretical displacement of 20 cm³/rev and runs at 1500 rpm. What is its theoretical flow rate in litres per minute?

  1. 20 L/min
  2. 45 L/min
  3. 15 L/min
  4. 30 L/min Correct answer.

Explanation

Theoretical flow is displacement times rotational speed: 20 cm³/rev × 1500 rev/min = 30,000 cm³/min, which equals 30 L/min. This assumes 100% volumetric efficiency, so actual flow would be slightly lower.

Question 31Fluid Power Fundamentals

In a hydraulic system, what is the primary function of a reservoir?

  1. To convert mechanical energy into fluid power
  2. To store fluid, allow contaminants to settle, and dissipate heat Correct answer.
  3. To pressurize the fluid before it enters the pump
  4. To filter out particles smaller than 10 micrometres

Explanation

The reservoir holds the system fluid, provides a residence time for air and contaminants to separate, and helps dissipate heat. It is normally vented or lightly pressurized but is not the primary pressure source.

Question 32Fluid Power Fundamentals

Which statement correctly describes the relationship between force, pressure, and area in a hydraulic actuator?

  1. Area equals pressure multiplied by force
  2. Force equals pressure divided by effective area
  3. Force equals pressure multiplied by effective area Correct answer.
  4. Pressure equals force multiplied by effective area

Explanation

The fundamental hydraulic relationship is F = p × A, where F is force, p is pressure, and A is the effective piston area. This equation underlies the force capability of any fluid power actuator.

Question 33Fluid Power Fundamentals

Which of the following is a typical consequence of using hydraulic oil with excessively high viscosity in a system?

  1. Increased compressibility and faster response
  2. Reduced internal leakage and lower pressure losses
  3. Increased resistance to flow and higher pressure losses Correct answer.
  4. Improved heat dissipation and lower operating temperature

Explanation

High viscosity increases internal friction in the fluid, raising flow resistance and pressure drop through conductors and valves. It can also cause poor suction performance and higher mechanical losses.

Question 34Fluid Power Fundamentals

A hydraulic cylinder with a piston area of 0.005 m² must produce a force of 25 kN. What pressure is required?

  1. 50 MPa
  2. 0.5 MPa
  3. 125 MPa
  4. 5 MPa Correct answer.

Explanation

Pressure is force divided by area: 25,000 N / 0.005 m² = 5,000,000 Pa, or 5 MPa. This is a moderate hydraulic pressure, well within typical system ratings.

Question 35Fluid Power Fundamentals

A hydraulic motor has a displacement of 50 cm³/rev and receives 30 L/min. What is its theoretical output speed?

  1. 300 rpm
  2. 1500 rpm
  3. 600 rpm Correct answer.
  4. 1000 rpm

Explanation

Theoretical speed is flow divided by displacement: 30,000 cm³/min ÷ 50 cm³/rev = 600 rev/min. Volumetric losses would make the actual speed slightly lower.

Question 36Fluid Power Fundamentals

Which statement best describes the function of a pressure-compensated pump in a hydraulic system?

  1. It maintains constant displacement regardless of pressure
  2. It increases flow as system pressure rises
  3. It converts fluid power into mechanical power
  4. It reduces its displacement as system pressure approaches a set value Correct answer.

Explanation

A pressure-compensated pump adjusts its displacement to hold system pressure near a set point, reducing flow as pressure rises. This limits power consumption and heat generation when the actuator is stalled or unloaded.

Question 37Fluid Power Fundamentals

In a hydraulic circuit, what is the purpose of a directional control valve?

  1. To remove particulate contamination from the fluid
  2. To store energy for peak demand
  3. To start, stop, and change the direction of fluid flow Correct answer.
  4. To limit the maximum pressure in the circuit

Explanation

Directional control valves route fluid to different ports to start, stop, or reverse actuator motion. They are characterized by the number of positions and the number of flow paths.

Question 38Fluid Power Fundamentals

A hydraulic system delivers 40 L/min at a pressure of 100 bar. Neglecting losses, what hydraulic power is being transmitted?

  1. 4.0 kW
  2. 2.4 kW
  3. 6.7 kW Correct answer.
  4. 10.0 kW

Explanation

Hydraulic power is P = p × Q. Using p = 100 bar = 10,000,000 Pa and Q = 40 L/min = 0.000667 m³/s, power = 10,000,000 × 0.000667 ≈ 6,667 W, or about 6.7 kW. A shortcut is kW = bar × L/min ÷ 600.

Question 39Fluid Power Fundamentals

What does the term 'volumetric efficiency' of a hydraulic pump describe?

  1. The ratio of mechanical power out to fluid power in
  2. The ratio of actual flow delivered to theoretical flow Correct answer.
  3. The ratio of fluid temperature rise to input power
  4. The ratio of output pressure to input pressure

Explanation

Volumetric efficiency is actual output flow divided by theoretical displacement times speed. It reflects internal leakage and fluid compressibility losses within the pump.

Question 40Fluid Power Fundamentals

Which of the following best explains why hydraulic systems can produce large forces from compact actuators?

  1. Hydraulic fluid has very low density, reducing inertial losses
  2. Hydraulic fluid lubricates moving parts, eliminating friction
  3. Hydraulic fluid transmits pressure equally in all directions, allowing high pressure over a small area Correct answer.
  4. Hydraulic fluid is highly compressible, storing energy for sudden release

Explanation

Pascal's principle states that pressure applied to a confined fluid is transmitted undiminished throughout. A small pump pressure acting on a larger piston area produces a large force, enabling compact high-force actuators.

Question 41Fluid Power Fundamentals

A hydraulic cylinder has a bore of 50 mm and a rod diameter of 25 mm. What is the approximate effective area on the rod side during extension?

  1. 1963 mm²
  2. 1473 mm² Correct answer.
  3. 2454 mm²
  4. 490 mm²

Explanation

The annulus area is (π/4)(D² − d²) = (π/4)(50² − 25²) = (π/4)(2500 − 625) = (π/4)(1875) ≈ 1473 mm². This is the area that fluid acts on during rod-side pressurization.

Question 42Fluid Power Fundamentals

Which statement about the relationship between flow rate, actuator area, and actuator speed is correct?

  1. Speed equals effective area divided by flow rate
  2. Speed equals flow rate divided by effective area Correct answer.
  3. Speed equals flow rate multiplied by effective area
  4. Speed equals pressure divided by flow rate

Explanation

For a hydraulic actuator, piston speed v = Q / A, where Q is flow rate and A is the effective area. Increasing flow or decreasing area increases speed.

Question 43Fluid Power Fundamentals

What is the primary purpose of an accumulator in a hydraulic system?

  1. To cool the hydraulic fluid by increasing surface area
  2. To store pressurized fluid and release it to meet peak demand or absorb pulsation Correct answer.
  3. To increase the maximum pressure available from the pump
  4. To filter out fine particles from the hydraulic oil

Explanation

An accumulator stores energy in the form of pressurized fluid or gas and can supplement pump flow during peaks, absorb pressure surges, or maintain pressure when the pump is unloaded.

Question 44Fluid Power Fundamentals

Which factor most directly determines the pressure drop across a hydraulic orifice at a given flow rate?

  1. The length of the conductor downstream
  2. The orifice area and the fluid density Correct answer.
  3. The fluid viscosity alone
  4. The reservoir fluid level

Explanation

For turbulent flow through an orifice, pressure drop is proportional to fluid density and the square of flow rate, and inversely proportional to the square of orifice area. Viscosity has a secondary effect at low Reynolds numbers.

Question 45Fluid Power Fundamentals

A hydraulic pump delivers 50 L/min at 150 bar. If the pump's overall efficiency is 85%, what input power is required?

  1. 17.6 kW
  2. 10.6 kW
  3. 12.5 kW
  4. 14.7 kW Correct answer.

Explanation

Hydraulic output power is p × Q = 150 bar × 50 L/min ÷ 600 ≈ 12.5 kW. Input power is output divided by efficiency: 12.5 / 0.85 ≈ 14.7 kW.

Question 46Fluid Power Fundamentals

Which statement best describes the difference between laminar and turbulent flow in a hydraulic conductor?

  1. Laminar flow always has higher pressure loss than turbulent flow at the same flow rate
  2. Laminar flow has a flat velocity profile, while turbulent flow has a parabolic profile
  3. Laminar flow occurs only at high velocities, while turbulent flow occurs at low velocities
  4. Laminar flow is orderly and layered, while turbulent flow is chaotic with mixing Correct answer.

Explanation

Laminar flow consists of smooth, parallel layers with a parabolic velocity profile. Turbulent flow is characterized by chaotic eddies and mixing, typically occurring above a critical Reynolds number.

Question 47Fluid Power Fundamentals

In a hydraulic system, what is the primary function of a pressure relief valve?

  1. To control the direction of actuator movement
  2. To maintain a constant flow rate regardless of pressure
  3. To remove air from the hydraulic fluid
  4. To limit the maximum system pressure by diverting excess flow to the reservoir Correct answer.

Explanation

A pressure relief valve opens when system pressure reaches a set value, diverting flow to the reservoir and preventing overpressure. It is a safety and limiting device, not a continuous flow controller.

Question 48Fluid Power Fundamentals

A hydraulic cylinder extends at 0.1 m/s with a piston area of 2000 mm². What flow rate is required?

  1. 20 L/min
  2. 120 L/min
  3. 2 L/min
  4. 12 L/min Correct answer.

Explanation

Flow equals area times velocity: Q = 2000 mm² × 0.1 m/s = 0.002 m² × 0.1 m/s? Wait, 2000 mm² = 0.002 m², so Q = 0.002 × 0.1 = 0.0002 m³/s = 12 L/min. The calculation confirms 12 L/min.

Question 49Fluid Power Fundamentals

Which statement best explains why hydraulic fluid is typically considered nearly incompressible in system modelling?

  1. Its viscosity is low, so it flows easily under pressure
  2. Its specific heat is high, so it resists temperature change
  3. Its bulk modulus is very high, so volume change is small under normal pressures Correct answer.
  4. Its density decreases significantly with pressure

Explanation

Hydraulic oil has a high bulk modulus, meaning a large pressure change produces only a small fractional volume change. This near-incompressibility allows stiff, precise actuation and simplifies system equations.

Question 50Fluid Power Fundamentals

A hydraulic circuit uses a fixed-displacement pump with a relief valve set at 200 bar. The actuator stalls, and all pump flow passes over the relief valve at 200 bar. If pump flow is 20 L/min, what is the approximate heat generation in the relief valve?

  1. 4.0 kW
  2. 6.7 kW Correct answer.
  3. 10.0 kW
  4. 2.0 kW

Explanation

All hydraulic power is dissipated as heat when flow passes over the relief valve at the set pressure. Power = p × Q = 200 bar × 20 L/min ÷ 600 ≈ 6.7 kW, which would rapidly heat the fluid unless cooled.