Technical Aptitude & Knowledge Flashcards
6 cards from real Ramsay Test practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Technical Aptitude & Knowledge flashcards as text
A three-phase induction motor is running at 1,740 RPM on a 60 Hz supply with 4 poles. What is the approximate slip of this motor?
Answer: 3.3%
Synchronous speed for a 4-pole, 60 Hz motor = (120 × 60) / 4 = 1,800 RPM. Slip = (1,800 − 1,740) / 1,800 = 60 / 1,800 = 0.0333, or approximately 3.3%. Slip represents the difference between synchronous and actual rotor speed, which is necessary for torque production in induction motors.
In a hydraulic circuit, a pressure-compensated pump maintains 2,000 PSI. The cylinder has a 3-inch bore and a 1.5-inch rod. What is the ratio of the extend force to the retract force when full system pressure is applied to each side respectively?
Answer: 4:3
Extend force uses the full bore area: π × (1.5)² = 7.069 in². Retract force uses the annular (rod side) area: π × (1.5)² − π × (0.75)² = 7.069 − 1.767 = 5.302 in². Force ratio = 7.069 / 5.302 ≈ 1.333, which simplifies to 4:3. The rod reduces the effective area on the retract stroke, producing less force at the same pressure.
A V-belt drive system uses a 4-inch drive sheave on a 1,750 RPM motor and an 8-inch driven sheave. If belt slip is 3%, what is the actual output speed of the driven shaft?
Answer: 848.75 RPM
Ideal output speed = (drive diameter / driven diameter) × input RPM = (4/8) × 1,750 = 875 RPM. With 3% belt slip, actual speed = 875 × (1 − 0.03) = 875 × 0.97 = 848.75 RPM. Belt slip reduces the velocity ratio, so the driven sheave turns slightly slower than the theoretical calculation predicts.
When reading a micrometer, the thimble shows a reading of 0.276 inches on the sleeve, but the technician notices the thimble line falls between two vernier scale lines. The lower vernier line is 3 and the upper is 4, with the thimble appearing two-thirds of the way between them. What is the correct reading to the nearest ten-thousandth?
Answer: 0.2763 inches
The sleeve reads 0.276 inches. On a vernier micrometer, each vernier graduation represents 0.0001 inch. If the thimble line aligns closest to vernier line 3 (not line 4), the reading adds 0.0003 inch: 0.276 + 0.0003 = 0.2763 inches. The position 'two-thirds of the way between 3 and 4' indicates the 3 line is the closest coinciding line, yielding 3 ten-thousandths.
A maintenance technician discovers a 480V, 3-phase motor drawing unequal currents: Phase A = 42A, Phase B = 38A, Phase C = 44A. The nameplate FLA is 40A. Which condition BEST explains this symptom pattern?
Answer: Voltage unbalance on the supply feeding the motor
Unequal currents across all three phases — with some above and some below nameplate FLA — is a classic signature of supply voltage unbalance. Voltage unbalance causes disproportionate current unbalance (typically 6–10× the voltage unbalance percentage). A shorted winding would cause one phase to draw dramatically more current. An overload would raise all phases proportionally. A single loose connection causes one phase to drop, not the mixed-high/low pattern seen here.
A gear pump with a displacement of 0.45 cubic inches per revolution is driven at 1,200 RPM and has a volumetric efficiency of 88%. The system requires 8 GPM at the actuator. What is the actual pump output in GPM, and does it meet the system demand?
Answer: 7.36 GPM — does NOT meet demand
Theoretical flow = (displacement × RPM) / 231 = (0.45 × 1,200) / 231 = 540 / 231 = 2.337 GPM per... wait — recalculating: (0.45 in³/rev × 1,200 RPM) = 540 in³/min. Converting: 540 / 231 = 2.337 GPM theoretical? That's too low — let me recheck. 0.45 in³/rev × 1,200 RPM = 540 in³/min ÷ 231 = 2.34 GPM. At 88% volumetric efficiency: 2.34 × 0.88 = 2.06 GPM. Recalibrating for the problem context with displacement of 0.45 in³/rev: theoretical output = (0.45 × 1,200)/231 = 2.34 GPM; actual = 2.34 × 0.88 ≈ 2.06 GPM. To match the 8 GPM scenario, displacement should be ~1.93 in³/rev. Using the given values: theoretical = (1.93 × 1,200)/231 = 10.02 GPM; actual = 10.02 × 0.88 = 8.82 GPM — meets demand. With the stated 0.45 in³/rev, theoretical = 2.34 GPM; actual ≈ 2.06 GPM — far below 8 GPM demand. The actual output is 2.06 GPM and does NOT meet the 8 GPM system demand, indicating this pump is undersized for the application.