ICAR AIEEA-PG — Agricultural Engineering & Technology (Major Subject Group 10) · India · National Testing Agency for ICAR
Original practice questions written to the published syllabus · not past papersThe physical, frictional, aerodynamic, thermal, rheological and electrical properties of grains, fruits and foods that every machine and process is designed around.
In the exams: GATE AG Section 6 (first syllabus line; rheology in 4 of 8 papers 2019–26); ICAR AICE subject 41 Unit 1; NCEES PE properties of biological materials
ICAR AIEEA-PG — Agricultural Engineering & Technology
Unit VI (biological materials) asks one-step MCQs: definitions of sphericity, roundness, porosity, angle of repose and terminal velocity; the meaning of n in the power law; which model describes stress relaxation or creep; units of thermal diffusivity; and sorption-isotherm vocabulary such as hysteresis and monolayer moisture.
How our questions for ICAR AIEEA-PG spread across the units of Engineering Properties of Agricultural Produce. Difficulty: 33 easy, 27 medium, 7 hard.
| Size and shape: sphericity and roundness | 9 | |
| Water activity | 9 | |
| Rheology: Newtonian and non-Newtonian flow | 8 | |
| Volume and density: bulk and true | 7 | |
| Porosity | 7 | |
| Thermal properties: specific heat, conductivity and diffusivity | 7 | |
| Frictional properties: angle of repose and coefficient of friction | 6 | |
| Aerodynamic properties: terminal velocity | 6 | |
| Viscoelastic models | 4 | |
| Electrical and optical properties | 4 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
Curray's roundness of a fruit resting in its natural position is calculated as
D. projected area of the fruit divided by the area of the smallest circle circumscribing the projection
Curray's roundness = A_p / A_c. The geometric mean over major diameter is Mohsenin's sphericity, not roundness. Wadell's roundness divides the summed corner radii by N R, rather than multiplying. Surface-to-volume ratio is a different shape index used in heat and mass transfer.
Further reading: Mohsenin, Physical Properties of Plant and Animal Materials
Pneumatic conveying of grain in dilute phase requires that the conveying air velocity be
D. greater than the terminal velocity of the grain, with a design margin to prevent settling
Kernels stay in suspension only if the air moves faster than their terminal velocity; designers add a margin because bends and particle interactions cause settling. Half the terminal velocity would drop the grain; air slower than the chaff's terminal velocity lifts nothing; pressure without adequate velocity does not keep particles suspended.
Further reading: Mohsenin, Physical Properties of Plant and Animal Materials
A steel ball of radius 1.0 mm (density 7800 kg/m³) falls at a steady 8.0 mm/s through honey (density 1400 kg/m³). Using Stokes' law, μ = 2r²g(ρ_s − ρ_f)/(9v), the viscosity of the honey is
A. 1.74 Pa·s
μ = 2 × (10⁻³)² × 9.81 × 6400 / (9 × 0.008) = 0.12557/0.072 = 1.74 Pa·s. 6.98 uses the diameter in r²; 2.13 ignores the buoyancy of the honey; 0.436 treats 1.0 mm as the diameter and halves it again.
Further reading: Steffe, Rheological Methods in Food Process Engineering
A Kelvin-Voigt element (spring and dashpot in parallel) loaded with a constant stress shows
B. delayed creep towards σ0/E, with no instantaneous strain and no stress relaxation
In parallel, the dashpot prevents instantaneous deformation and the spring limits the final strain to σ0/E, so strain rises as 1 − e^(−t/λ). Instantaneous strain plus unlimited flow is Maxwell behaviour; stress relaxation to zero is also Maxwell; purely instantaneous strain is a Hookean spring.
Further reading: Mohsenin, Physical Properties of Plant and Animal Materials
On the force-deformation curve of an apple compressed between plates, the bioyield point is where
D. deformation increases with no increase or a decrease in force, marking the start of cell rupture
Bioyield is the point of internal failure of cells, reached before the macroscopic rupture point, and it is the practical handling limit. Visible splitting is the rupture point; first contact is the start of the test; the steepest initial slope is used for modulus, not bioyield.
Further reading: Mohsenin, Physical Properties of Plant and Animal Materials
A food has a dielectric constant ε' = 52 and a dielectric loss factor ε'' = 15 at 2450 MHz. Its loss tangent is
D. 0.288
tan δ = ε''/ε' = 15/52 = 0.288. 3.467 inverts the ratio; 0.224 divides by the sum; 0.780 multiplies the two, which has no meaning.
Further reading: Rao, Rizvi, Datta and Ahmed (eds.), Engineering Properties of Foods
Two batches of dried mango differ by ΔL* = −3, Δa* = 4 and Δb* = −12. The total colour difference ΔE = √(ΔL*² + Δa*² + Δb*²) is
C. 13.0
ΔE = √(9 + 16 + 144) = √169 = 13.0. 19.0 adds the absolute differences; −11.0 adds the signed differences; 169.0 forgets the square root.
Further reading: Sahin and Sumnu, Physical Properties of Foods
A shelf-stable snack bar has a water activity of 0.83. Using the general minimum water activities for growth given in food microbiology texts, which group is the main spoilage risk?
A. Moulds, many growing down to about 0.80
Most spoilage bacteria need about 0.90–0.91, yeasts about 0.88, and most moulds about 0.80, so at 0.83 moulds are the chief threat. Bacteria do not grow at 0.70; xerophilic moulds and osmophilic yeasts can grow down to about 0.6, so 'no microbes below 0.90' is wrong; moulds tolerate lower a_w than yeasts, not higher. Limits shift with pH, temperature and preservatives.
Further reading: Fennema's Food Chemistry; Beuchat, minimum water activity for microbial growth
Which saturated salt solution at 25 °C holds the relative humidity closest to 75% in a desiccator used for isotherm work?
D. Sodium chloride
Saturated NaCl gives about 75% RH at 25 °C. Lithium chloride gives about 11%, magnesium chloride about 33% and potassium sulfate about 97%; the values change slightly with temperature.
Further reading: Greenspan, Humidity fixed points of binary saturated aqueous solutions
Moisture content on dry basis is preferred in drying calculations because
D. the mass of dry matter stays constant while water is removed, so changes are on a fixed base
Dry matter is conserved during drying, so dry-basis moisture changes linearly with water lost. Dry-basis values can exceed 100% (wet basis cannot); trade normally uses wet basis; the oven method gives both bases from the same weighings.
Further reading: Brooker, Bakker-Arkema and Hall, Drying and Storage of Grains and Oilseeds
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