Agricultural and Biosystems Engineers Licensure Examination (ABELE) · Philippines · Professional Regulatory Board of Agricultural and Biosystems Engineering, PRC
Original practice questions written to the published syllabus · not past papersWhere the energy for farm work comes from, how much is available, and how mechanisation is measured.
In the exams: GATE AG Section 3 Sources of Power; ICAR AIEEA-PG Unit V; PRC ABE power and machinery (32%)
How our questions for Agricultural and Biosystems Engineers Licensure Examination spread across the units of Farm Power Sources. Difficulty: 6 easy, 22 medium, 16 hard.
| Electrical power on the farm | 9 | |
| Solar power as a farm power source | 7 | |
| Animal draught power and harnessing | 6 | |
| Mechanical power: engines and tractors | 6 | |
| Wind power as a farm power source | 5 | |
| Biomass and biofuels as power sources | 5 | |
| Human power and its limits | 3 | |
| Farm power availability (kW/ha) | 2 | |
| Mechanisation indices | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
An animal-drawn mouldboard plough cuts a furrow 20 cm wide and 12 cm deep in a soil with a specific draught of 4 N/cm². What is the draught?
B. 960 N
Draught = specific draught × furrow area = 4 N/cm² × (20 × 12) cm² = 960 N. The other options are decimal slips or half the area; always multiply width by depth in the same units as the specific draught.
A diesel engine delivers 30 kW brake power while consuming 8 L/h of fuel (density 0.84 kg/L, calorific value 42 MJ/kg). What is its brake thermal efficiency?
B. 38.3%
Fuel energy rate = 8 × 0.84 × 42 = 282.24 MJ/h = 78.4 kW. Efficiency = 30/78.4 = 38.3%. Ignoring density gives 32.1%; dividing by density instead of multiplying gives 27.0%. 3.83% is a factor-of-ten slip.
A 4-pole induction motor runs on a 50 Hz supply with 4% slip at full load. What is its rotor speed?
B. 1440 rpm
Ns = 120f/p = 120 × 50/4 = 1500 rpm; N = Ns(1 − s) = 1500 × 0.96 = 1440 rpm. 1500 rpm is synchronous speed; 2880 rpm uses pole pairs instead of poles; adding slip gives 1560 rpm.
At a hot, elevated site the air density is 1.10 kg/m³ instead of the standard 1.225 kg/m³. By how much is the power in the wind reduced at the same wind speed?
D. 10.2%
Power is proportional to density: 1.10/1.225 = 0.8980, a reduction of 10.2%. Cubing the density ratio applies the speed rule to density (27.6%); 11.4% uses the wrong base. 19.4% squares the density ratio (1 − 0.898²).
A 300 W crystalline silicon module has a power temperature coefficient of −0.4%/°C. Estimate its output at 1000 W/m² when the cell temperature is 55 °C.
D. 264 W
Rise above STC = 55 − 25 = 30 °C; loss = 30 × 0.4% = 12%; P = 300 × 0.88 = 264 W. Using 55 °C instead of the rise gives 234 W; adding the loss gives 336 W; 36 W is the loss, not the output.
A farm has 8 cattle each giving 10 kg of fresh dung per day. Taking a gas yield of 0.04 m³ per kg of fresh dung, what daily biogas production can be expected?
C. 3.2 m³/day
Dung = 8 × 10 = 80 kg/day; gas = 80 × 0.04 = 3.2 m³/day. 0.4 m³ is for one animal only. 0.32 and 32 m³/day are factor-of-ten slips.
The same 80 kg/day of dung is mixed 1:1 with water (slurry density about 1000 kg/m³). For a hydraulic retention time of 40 days, what digester volume is needed?
B. 6.4 m³
Slurry = 80 + 80 = 160 kg/day ≈ 0.16 m³/day; volume = 0.16 × 40 = 6.4 m³. Forgetting the water gives 3.2 m³; 0.16 m³ is one day's feed only. 64 m³ is a factor-of-ten slip.
A farmer wants to run an unmodified diesel pump set on biogas. What is the realistic arrangement?
C. Dual-fuel operation, with a small pilot injection of diesel to ignite the gas
Methane has high auto-ignition resistance and will not ignite by compression alone in a diesel engine, so a pilot diesel injection is used; this saves much, but not all, of the diesel. Spark-ignition engines can run on biogas alone.
Custom hiring centres (machinery banks) mainly raise the farm power effectively available to smallholders by:
C. Letting many farmers use machines they could not justify owning, when they need them
Hiring spreads fixed costs over more farms and hours, improving access and timeliness without each farmer buying a machine. It does not change machine ratings.
Two reports give very different 'levels of mechanisation' for the same state. What should you check first?
D. The definition used (power share, operation-wise area, energy share or stock) and the area and data year
There is no single agreed index: power-based, operation-based, energy-based and stock-based measures can differ widely. Compare like with like on definition, area basis and year before judging.
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