NCED Hydraulic & Pneumatic Systems 2 — Questions and Answers
Question 1: Pascal's Law states that pressure applied to a confined fluid is transmitted:
- Only downward due to gravity
- Equally in all directions (Correct answer)
- Only to the nearest surface
- Proportionally to the fluid's viscosity
Correct answer: Equally in all directions
Pascal's Law states that pressure applied to a confined, incompressible fluid is transmitted equally and undiminished in all directions.
Question 2: In a hydraulic system, if a piston with a 2 sq in area receives 500 psi, what force is exerted?
- 250 lbs
- 500 lbs
- 1000 lbs (Correct answer)
- 2000 lbs
Correct answer: 1000 lbs
Force equals pressure multiplied by area (F = P × A), so 500 psi × 2 sq in = 1000 lbs.
Question 3: Which property of hydraulic fluid most directly affects system efficiency at high temperatures?
- Color
- Viscosity (Correct answer)
- Density
- Electrical conductivity
Correct answer: Viscosity
Viscosity decreases as temperature rises, causing leakage past seals and reduced pump efficiency in hydraulic systems.
Question 4: A double-acting hydraulic cylinder differs from a single-acting cylinder in that it:
- Uses two separate hydraulic fluids
- Can exert force in both extension and retraction strokes (Correct answer)
- Operates at twice the pressure
- Contains two pistons in series
Correct answer: Can exert force in both extension and retraction strokes
A double-acting cylinder has hydraulic ports on both sides of the piston, allowing pressurized fluid to drive the rod in both directions.
Question 5: What is the primary purpose of a hydraulic accumulator?
- Filter contaminants from the fluid
- Store pressurized fluid for supplemental flow or energy recovery (Correct answer)
- Regulate system temperature
- Convert rotary motion to linear motion
Correct answer: Store pressurized fluid for supplemental flow or energy recovery
A hydraulic accumulator stores pressurized fluid that can be released to supplement pump flow during peak demand or recover energy.
Question 6: Which type of hydraulic pump is most commonly used in high-pressure industrial systems due to its efficiency?
- Gear pump
- Vane pump
- Piston pump (Correct answer)
- Centrifugal pump
Correct answer: Piston pump
Piston pumps can achieve very high pressures (3000–6000 psi) and maintain high volumetric efficiency, making them preferred for demanding industrial applications.
Question 7: In hydraulic circuit diagrams, what does a dashed line typically represent?
- Main pressure line
- Drain or pilot line (Correct answer)
- Electrical signal
- Mechanical connection
Correct answer: Drain or pilot line
Dashed lines in hydraulic schematics represent drain lines, pilot lines, or case drain lines carrying low-pressure return fluid.
NCED Hydraulic & Pneumatic Systems 2
Pascal's Law states that pressure applied to a confined fluid is transmitted: