ASRB NET — Farm Machinery & Power / Land & Water Management Engineering / Agricultural Structures & Process Engineering · India · Agricultural Scientists Recruitment Board (ICAR)
Original practice questions written to the published syllabus · not past papersSolar thermal, solar PV, wind and micro-hydro for farms, from sun geometry to sizing a solar pump.
In the exams: GATE AG Section 3 (solar PV in 5 of 8, wind in 5 of 8 papers 2019–26); ICAR AIEEA-PG Unit V; ICAR AICE subject 42 Units 4, 5 and 7; NCEES PE energy sources
ASRB NET — Farm Machinery & Power
Theory-heavy MCQs on renewable energy in agriculture: solar thermal devices and their tests, PV system components, windmill types and solidity, micro-hydro turbines.
How our questions for ASRB NET spread across the units of Renewable Energy Sources (Solar, Wind). Difficulty: 25 easy, 15 medium, 0 hard.
| Energy scenario | 6 | |
| Measurement of solar radiation | 4 | |
| Wind turbines and water-pumping windmills | 4 | |
| Solar radiation geometry | 3 | |
| Flat-plate collectors and their efficiency | 3 | |
| Concentrating collectors | 3 | |
| Solar dryers, cookers, water heaters and stills | 3 | |
| Photovoltaic cell physics and the I-V curve | 3 | |
| Energy storage | 3 | |
| Solar pumps and agri-voltaics | 2 | |
| Power in the wind and the Betz limit | 2 | |
| Micro-hydro | 2 | |
| Fill factor and MPPT | 1 | |
| PV system sizing: on-grid and off-grid | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
One kilowatt-hour of energy is equal to:
B. 3.6 MJ
1 kWh = 1000 W × 3600 s = 3.6 × 10⁶ J = 3.6 MJ. 3.6 kJ is the energy of 1 W for an hour (1 Wh), a factor-of-1000 slip. 36 MJ is a factor-of-ten slip.
Which of the following is a renewable (flow) energy source rather than a stock?
C. Wind
Wind is continually replenished by solar heating of the atmosphere. Coal, natural gas and uranium are stocks laid down over geological time and used far faster than they form.
Which instrument measures beam (direct normal) solar radiation?
A. Pyrheliometer
A pyrheliometer is a collimating tube pointed at the sun on a tracker, so it sees only the sun's disc and a narrow ring around it. A pyranometer sees the whole hemisphere (global radiation); the Campbell–Stokes recorder gives sunshine hours; an anemometer measures wind speed.
Anti-islanding protection in a grid-connected PV inverter:
B. Disconnects the inverter when the grid fails, so the system does not energise lines being repaired
An 'island' is a section of network kept live by local generators after the grid has gone down; it endangers line workers. Grid-tied inverters must shut down on loss of grid, which is why an ordinary on-grid system without battery backup gives no power in an outage.
In most farm solar pumping systems, energy for cloudy periods is stored mainly as:
C. Water in an elevated tank or reservoir
Storing water is far cheaper and longer-lived than storing electricity, so most solar pumps are battery-less and directly coupled through a controller, with a tank or the soil profile buffering supply.
The Betz limit, the maximum fraction of wind power that any open rotor can extract, is:
D. 16/27 ≈ 0.593
Momentum theory gives Cp = 4a(1 − a)², maximised at a = 1/3, where Cp = 16/27 ≈ 0.593. 2/3 is the velocity ratio at the rotor at that condition and 1/3 is the induction factor, not the power coefficient.
In a run-of-river micro-hydro scheme, the forebay is:
A. A tank at the penstock head that settles sediment and gives a steady water level at the penstock inlet
Water from the headrace enters the forebay, where sediment settles and a stable level prevents air being drawn into the penstock. The penstock is the pressure pipe, the tailrace returns water, and run-of-river schemes have no seasonal storage dam.
Why is the solar declination zero at the equinoxes?
C. The sun's rays are then parallel to the equatorial plane, so the noon sun is overhead at the equator
Declination is the angle between the sun–earth line and the equatorial plane; at the equinoxes this line lies in the equatorial plane. The earth's axial tilt does not change, and perihelion occurs in early January, not at an equinox.
In agricultural energy auditing, energy used to manufacture fertiliser and machinery is classified as:
C. Indirect energy input
Direct energy is used on the farm itself (diesel, electricity, human and animal labour); energy embodied in manufactured inputs such as fertiliser, pesticides and machinery is indirect. The coefficients used to value them come from a cited table and differ between sources.
The clearness index KT is defined as:
C. The ratio of global horizontal radiation to extraterrestrial horizontal radiation over the same period
KT = H/H0. It is used to correlate the diffuse fraction. n/N is the relative sunshine duration used in Ångström–Prescott, a different quantity.
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