Rajasthan PSC — Assistant Agriculture Engineer (Agriculture Engineering syllabus) · India · Rajasthan Public Service Commission
Original practice questions written to the published syllabus · not past papersHow tractor engines work and how their performance is measured — the single most reliably examined farm-power topic.
In the exams: GATE AG Section 3 (engine performance asked in all 8 papers 2019–26); ICAR AIEEA-PG Unit V; ICAR AICE subject 39 Unit 4; NCEES PE IC engines; RPSC AAE
Rajasthan PSC Assistant Agriculture Engineer and other state services
Practical systems knowledge: fuel system and bleeding, cooling and lubrication faults, battery and starter, governing, maintenance schedules and the basic performance formulas.
How our questions for Rajasthan PSC spread across the units of Tractor & Automotive Engines (IC Engines). Difficulty: 36 easy, 10 medium, 0 hard.
| Ignition and electrical system: battery, starter and alternator | 6 | |
| Engine classification and terminology | 4 | |
| Two-stroke and four-stroke engines | 4 | |
| Engine components | 4 | |
| Diesel fuel system: injection pump and injector | 4 | |
| Combustion and knock | 4 | |
| Air intake and turbocharging | 4 | |
| Cooling system | 4 | |
| Lubrication system and lubricants | 3 | |
| Fuel properties | 3 | |
| Otto, Diesel and dual cycles | 1 | |
| Governing | 1 | |
| Engine performance: IP, BP, FP and efficiencies | 1 | |
| BSFC and heat balance | 1 | |
| Engine testing | 1 | |
| Emission norms | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
Compression ratio of a reciprocating engine is defined as
A. (swept volume + clearance volume) ÷ clearance volume
r = total volume at BDC ÷ volume at TDC = (Vs + Vc)/Vc. Vs/Vc is r − 1, a common slip; the ratio of pressures is not the compression ratio.
Further reading: Ganesan, Internal Combustion Engines
A three-cylinder tractor engine has a bore of 95 mm and a stroke of 110 mm. Its total displacement is closest to
D. 2.34 L
Per cylinder Vs = (π/4)(9.5)²(11) = 779.7 cm³; × 3 = 2339 cm³ = 2.34 L. 0.78 L is one cylinder only; 9.36 L forgets the π/4 factor. Swapping bore and stroke gives (π/4)(11)²(9.5) × 3 = 2.71 L.
A common firing order for an in-line four-cylinder four-stroke engine is
D. 1-3-4-2
1-3-4-2 (or 1-2-4-3) spreads loads along the crankshaft. 1-5-3-6-2-4 is a six-cylinder order.
The ring fitted lowest on a diesel piston, with slots or holes behind it, is the
D. oil-control (scraper) ring
The oil-control ring scrapes surplus oil off the wall and returns it through holes in its groove. Compression rings above it seal the gas.
A tractor runs its tank dry and will not restart after refuelling. The first thing to do is
B. bleed air from the fuel system, starting at the filters and working toward the injectors
Air in the low-pressure circuit stops the pump building injection pressure. Bleed from the filters to the pump and then the injector pipes, so air is not pushed into sections already cleared.
Diesel knock is mainly caused by
B. a long ignition delay, so much fuel accumulates and then burns at once
Fuel injected during a long delay burns almost simultaneously in the rapid-combustion stage, giving a steep pressure rise. End-gas self-ignition is SI knock.
Further reading: Heywood, Internal Combustion Engine Fundamentals
A knapsack sprayer's two-stroke engine needs a 25:1 petrol-to-oil mixture. The oil to add to 5 L of petrol is
D. 200 mL
Oil = petrol ÷ 25 = 5000 mL/25 = 200 mL. 192 mL treats 25:1 as a fraction of the total mixture; always follow the ratio the maker specifies. 500 mL divides by 10 instead of 25.
Two 12 V, 100 Ah batteries are connected in series for a 24 V starting system. The combination provides
D. 24 V at 100 Ah
In series the voltages add and the ampere-hour capacity stays the same. In parallel the capacity would add (12 V, 200 Ah).
The governor normally fitted to an agricultural tractor diesel engine is
C. an all-speed governor
The tractor governor holds whatever speed the hand throttle sets, from idle to maximum, so PTO machines run steadily. Constant-speed governors are for generator sets; min–max governors were used on road vehicles. This is also called a variable-speed governor.
The two reference fuels originally used to define the cetane scale are
C. n-hexadecane (100) and alpha-methylnaphthalene (0)
Cetane (n-hexadecane) = 100 and alpha-methylnaphthalene = 0; current practice uses heptamethylnonane (15) as the low reference. Iso-octane/n-heptane define the octane scale.
Further reading: Heywood, Internal Combustion Engine Fundamentals
Ten here, 46 in the app. The Laisha app has every practice question we have written to Rajasthan PSC in this subject, marked as you go, with timed papers, a jump-to-unanswered list and a certificate when you pass at 70 per cent.
Free for ten days, then one subscription of US$10 a month. We would rather say so here than have you find it later.
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