NCEES PE Agricultural and Biological Engineering · USA · NCEES (ASABE is the content partner)
Original practice questions written to the published syllabus · not past papersNCEES PE Agricultural and Biological Engineering is a licensing and registration exam run by NCEES (ASABE is the content partner), for candidates in USA. Computer-based, 85 questions, 9.5-hour appointment (8.5 hours of exam). Once a year (next: 28 Oct 2026). Closed book with the electronic NCEES handbook and supplied searchable ASABE standards; SI and US customary units.
Source: ncees.org.
Checked against the exam body's published information. Formats and fees change; confirm the current edition there before you book.
Electrical circuits and electric motors appear under Common System Applications: motor input power and current from pump or fan duty, power-factor correction, voltage drop and conductor sizing for long farm runs, and sensors and data acquisition (bridges, 4–20 mA loops, ADC resolution). Livestock-facility questions can touch equipotential planes (ASABE EP473, a supplied standard).
Circuits, power, transformers, electronic devices and safe wiring: what a farm engineer needs before motors and sensors.
Our 27 NCEES PE Agricultural and Biological Engineering questions in this subject: 3 easy, 13 medium, 11 hard, across 10 units.
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
These 10 were written to NCEES PE Agricultural and Biological Engineering and are not shown on any other exam's page.
A North American farm receives a 120/240 V split-phase supply. What is the voltage between the two hot (line) conductors?
A. 240 V
In split-phase supply a centre-tapped transformer gives 120 V from each line to the neutral, and the two lines are 180° apart, so line to line is 240 V. 208 V is the line voltage of a 120/208 V three-phase star system, not split-phase. 0 V would apply only if the two lines were in phase.
An electrician disconnects an ammeter from a current transformer on a farm's main supply while the load is running. What is the hazard?
D. An open CT secondary develops a dangerous high voltage and the core overheats
A CT's primary current is set by the load, not by the secondary. With the secondary open, there is no opposing ampere-turns, the core flux rises greatly, a high and dangerous voltage appears at the secondary terminals and the core overheats. Always short the secondary before removing a meter. The primary current is unchanged and polarity does not reverse.
An electronic energy meter has a constant of 1600 impulses per kWh. Its LED flashes 40 times in 60 seconds. What is the average load?
D. 1.5 kW
Energy in 60 s = 40/1600 = 0.025 kWh; power = 0.025 kWh/(1/60 h) = 1.5 kW. 0.025 is energy in kWh, not power; multiplying by 3600 treats 60 s as one second; 0.667 kW inverts the ratio.
An average-responding (non-true-RMS) multimeter is used on the output of a variable-frequency drive feeding a pump motor. Why may its reading be wrong?
B. It assumes a sine wave, but the drive output is a distorted pulse waveform
Average-responding meters measure the rectified average and multiply by the sine-wave form factor of 1.11. A drive's pulse-width-modulated output is far from sinusoidal, so the scaling is wrong; a true-RMS meter rated for drive measurements is needed. The drive output is AC at variable frequency, not DC.
A quarter-bridge strain gauge on a bin load cell has gauge factor 2 and 10 V excitation. At 500 microstrain the bridge output is approximately V_ex·GF·ε/4. What amplifier gain gives 2.5 V at this strain?
C. 1000
Bridge output = 10 × 2 × 500 × 10⁻⁶/4 = 2.5 mV; gain = 2.5/0.0025 = 1000. Forgetting the /4 gives 250; using /2 (half bridge) gives 500; omitting the gauge factor gives 2000.
A comparator switches a borehole pump from a float-free level sensor, but the pump chatters on and off when the water is near the set level. What is the standard fix?
A. Add positive feedback (a Schmitt trigger) to give hysteresis
Near the threshold, noise and ripples make the input cross back and forth, so the output chatters. Positive feedback creates two thresholds (hysteresis), so the pump starts at one level and stops at another. Negative feedback removes the switching action entirely.
A soil-moisture sensor gives 0–5 V for 0–100 % volumetric moisture and is read by an 8-bit ADC with a 5 V reference. What is the smallest moisture change the ADC can resolve?
A. 0.391 % moisture
An 8-bit ADC has 2⁸ = 256 steps; 100 %/256 = 0.391 % per step (one step = 19.5 mV). 0.0977 % is the 10-bit figure; dividing by 8 bits gives 12.5 %; 19.5 is the step size in mV, not in % moisture. Resolution is not accuracy: sensor calibration usually limits the result more.
A 230 V single-phase supply to a pump shed 60 m away carries 20 A. The voltage drop must not exceed 3 %. Using copper ρ = 1.72 × 10⁻⁸ Ω·m and ignoring reactance, what is the minimum conductor size, and which standard size is chosen?
D. 5.98 mm², so 6 mm²
Allowed drop = 0.03 × 230 = 6.9 V. A = ρ × 2L × I/ΔV = 1.72 × 10⁻⁸ × 120 × 20/6.9 = 5.98 × 10⁻⁶ m², so the next larger standard size, 6 mm², is chosen. Using one-way length gives 2.99 mm²; rounding down to 4 mm² breaks the limit. Codes give tabulated mV/A/m values that include temperature and reactance, and current capacity must be checked too.
Dairy cows hesitate to drink from metal water bowls and milk yield falls; a few volts are measured between the bowls and the floor. What is the recognised engineering remedy?
B. Install an equipotential plane bonded to the metalwork
Stray voltage between metal that animals touch and the floor they stand on is controlled by an equipotential plane: reinforcing mesh in the floor bonded to the metal equipment so both stay at the same potential (ASABE EP473). Removing protective earth creates a shock hazard; an RCD does not remove a steady neutral-to-earth voltage.
During a power cut a farmer plans to plug a portable generator into a socket outlet to power the house. Why must a transfer (changeover) switch be used instead?
D. Without it the generator would backfeed and energise the line workers are repairing
Connecting a generator into house wiring without isolation lets it feed back through the service and transformer, making the supposedly dead network live and endangering line workers; it also damages the generator when supply returns. A transfer switch breaks the supply connection before connecting the generator.
This plan follows where our questions actually fall, so the time goes where the marks are likely to be. It is our reading of the syllabus, not the exam body's weighting.
Read the manual chapters for these first and do every worked question you can find on them.
Aim for one sitting per unit, then mixed questions across them.
Learn the definitions, classifications and standard numbers; these units are more often recalled than worked.
Come back to these after a first pass, untimed, and read every explanation, including for the options you rejected.
Do these early in revision so they are fast on the day.
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