GATE — Agricultural Engineering (AG) · India · IITs and IISc on rotation (2026: IIT Guwahati)
Original practice questions written to the published syllabus · not past papersHow tractors and implements are tested against codes, and how to read a test report.
In the exams: GATE AG Section 3 (tractor tests and performance); ICAR AIEEA-PG Unit V (test codes and procedure); ICAR AICE subject 39 Unit 3; ASRB NET FMP
GATE — Agricultural Engineering (AG)
Section 3 tractor tests and performance: numerical answers on PTO power from dynamometer readings, specific fuel consumption, drawbar power, wheel slip, tractive efficiency, torque backup and field capacity. Answers are sensitive to km/h versus m/s, litres versus kilograms of fuel, and slip measured on the loaded rather than unloaded revolutions.
How our questions for GATE spread across the units of Farm Machinery Testing, Evaluation & Standards. Difficulty: 6 easy, 21 medium, 8 hard.
| PTO performance test | 6 | |
| Drawbar performance test | 5 | |
| Test instrumentation: dynamometers and fuel meters | 5 | |
| Laboratory and field tests of tillage and sowing equipment | 5 | |
| Hydraulic lift test | 3 | |
| Tests of sprayers and harvesting equipment | 3 | |
| Brake and turning tests | 2 | |
| Noise at the operator's ear | 2 | |
| Interpreting test reports | 2 | |
| Types of tests: commercial, batch, confidential and prototype | 1 | |
| Test codes: OECD, BIS, PAES/PNS, ASABE and ISO | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
The OECD Standard Code that covers the performance testing of agricultural tractors — PTO, hydraulic and drawbar power and fuel consumption — is
A. Code 2
Code 2 is the performance code. Code 4 is the static ROPS test for standard tractors, Code 5 is noise at the driver's position, and Code 10 covers falling object protective structures.
During a PTO test the dynamometer records a torque of 220 N·m at a PTO speed of 540 rev/min. The PTO power is
B. 12.44 kW
P = 2πNT/60 = 2π × 540 × 220 / 60 = 12441 W = 12.44 kW. Leaving out the /60 gives 746.4 kW; using 1000 rev/min gives 23.04 kW; leaving out 2π gives 1.98 kW.
In a drawbar test a tractor pulls 25 kN at 7.2 km/h. The drawbar power is
B. 50.0 kW
P = pull × speed = 25 kN × 7.2/3.6 m/s = 25 × 2.0 = 50.0 kW. Forgetting to convert km/h gives 180 kW; dividing by 3.6 twice gives 13.9; dividing by 36 gives 5.0.
With no drawbar load a tractor advances 4.2 m per revolution of its driving wheels. Under a heavy load it advances 3.6 m per revolution. The wheel slip is
D. 14.3 %
Slip = (advance unloaded − advance loaded)/advance unloaded × 100 = (4.2 − 3.6)/4.2 × 100 = 14.3 %. Dividing by the loaded advance gives 16.7 %; 85.7 % is the travel ratio; 6.0 simply scales the difference.
Two independent noise sources each produce 86 dB(A) at the operator's ear. The combined level is
D. 89 dB(A)
L = 10 log₁₀(2 × 10^8.6) = 86 + 10 log₁₀ 2 = 89.0 dB(A). Decibels are not added arithmetically (172); a second equal source does add energy, so 86 is wrong; +6 dB applies to doubling sound pressure from coherent sources, not to two independent sources.
Three independent sources produce 84, 87 and 90 dB(A) at the driver's position. The combined level is
D. 92.4 dB(A)
L = 10 log₁₀(10^8.4 + 10^8.7 + 10^9.0) = 10 log₁₀(2.512e+08 + 5.012e+08 + 1.000e+09) = 92.4 dB(A). The arithmetic mean (87.0) and the loudest source alone (90) both ignore the added energy; the plain sum is meaningless.
A cultivator with a working width of 1.8 m operates at 4.5 km/h. Its theoretical field capacity is
A. 0.81 ha/h
TFC = w × v/10 = 1.8 × 4.5/10 = 0.81 ha/h (because 1 km × 1 m = 1000 m² = 0.1 ha). 8.1 omits the /10; 0.081 divides by 100; 2.25 wrongly converts to m/s.
A 3-bottom mouldboard plough, each bottom 30 cm wide, works at 18 cm depth with a measured draft of 12 kN. Its specific draft is
D. 7.41 N/cm²
Furrow area = 3 × 30 × 18 = 1620 cm². Specific draft = 12000 N/1620 cm² = 7.41 N/cm². Using one bottom's area gives 22.2; 0.741 is a decimal slip; 133 divides by total width alone, which is draft per cm of width.
A thresher is fed crop containing 500 kg of grain in total. Unthreshed grain collected from all outlets amounts to 6 kg. The threshing efficiency is
D. 98.8 %
Threshing efficiency = (1 − unthreshed/total) × 100 = (1 − 6/500) × 100 = 98.8 %. 1.2 % is the unthreshed fraction; 97.6 % subtracts the loss twice; 94.0 % subtracts the kilograms of unthreshed grain as if they were a percentage.
In a dynamometer, the casing is mounted on trunnion bearings and restrained by a torque arm. This arrangement allows
D. the casing's reaction torque to be measured by a load cell
Whatever torque the rotor applies to the casing (by water, magnetism or friction) tends to rotate the casing; the torque arm and load cell measure that reaction, which equals the shaft torque. The trunnions do not unload the engine, measure water flow, or affect governed speed.
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