WTMA Hydraulics and Fluid Dynamics 4 — Questions and Answers
Question 1: Two hydraulic cylinders are connected in parallel to the same pump. Compared to a single cylinder, what is true about force and speed?
- Force per cylinder is the same, but each extends at half the speed (Correct answer)
- Each cylinder exerts double the force at the same speed
- Force is halved and speed doubles
- Force and speed are both unchanged
Correct answer: Force per cylinder is the same, but each extends at half the speed
In parallel, pressure (and thus force) is the same, but pump flow is split, so each cylinder extends more slowly.
Question 2: What happens to system pressure when a hydraulic cylinder reaches the end of its stroke and cannot move further?
- Pressure rises until the relief valve opens (Correct answer)
- Pressure drops to zero
- Pressure stays constant
- Flow increases to compensate
Correct answer: Pressure rises until the relief valve opens
With no movement to absorb pump output, pressure builds rapidly until the relief valve opens to protect the system.
Question 3: Which factor most affects the viscosity of hydraulic oil in real-world operation?
- Temperature (Correct answer)
- Color of the fluid
- Size of the reservoir
- Hose diameter
Correct answer: Temperature
Viscosity drops significantly as temperature rises, which is why hydraulic systems specify oil grades for operating temperature ranges.
Question 4: A flow control valve is installed in a hydraulic circuit. Its primary function is to:
- Regulate the speed of a hydraulic actuator (Correct answer)
- Set the maximum system pressure
- Choose the direction of cylinder travel
- Remove air from the system
Correct answer: Regulate the speed of a hydraulic actuator
Flow control valves restrict or allow fluid flow to control actuator speed, not pressure or direction.
Question 5: Why is it important to bleed air from a hydraulic system?
- Air is compressible and causes spongy, unpredictable actuator movement (Correct answer)
- Air increases fluid viscosity
- Air raises system pressure dangerously
- Air causes the fluid to overheat rapidly
Correct answer: Air is compressible and causes spongy, unpredictable actuator movement
Trapped air compresses under pressure, creating a cushioning effect that makes cylinder movement feel soft and inconsistent.
Question 6: A gear pump operates by:
- Meshing gear teeth to trap and move fluid from inlet to outlet (Correct answer)
- Spinning an impeller to impart velocity to the fluid
- Using pistons reciprocating in cylinders to push fluid
- Flexing a diaphragm to displace fluid
Correct answer: Meshing gear teeth to trap and move fluid from inlet to outlet
Gear pumps use intermeshing gears to carry fluid in the spaces between teeth from the suction side to the discharge side.
Question 7: What is the primary purpose of a hydraulic filter?
- Remove contaminant particles that cause wear in valves and pumps (Correct answer)
- Regulate pressure throughout the system
- Cool the hydraulic fluid
- Prevent fluid from flowing backward
Correct answer: Remove contaminant particles that cause wear in valves and pumps
Filters remove solid particles from the fluid to prevent abrasive wear and clogging of precision hydraulic components.
WTMA Hydraulics and Fluid Dynamics 4
Two hydraulic cylinders are connected in parallel to the same pump.
Compared to a single cylinder, what is true about force and speed?