GATE AG flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Bulk density

Oven-dry mass of soil divided by its total volume, including pore space. Typical mineral soils range from 1.1 to 1.6 g/cm³; compaction raises it and reduces porosity.

Field capacity

Water content remaining in soil after free drainage has essentially stopped, usually about 2 to 3 days after saturation. It marks the upper limit of plant-available water.

Permanent wilting point

Soil water content at which plants can no longer extract water and remain wilted even in a humid atmosphere. Water below this point is unavailable to roots.

Kostiakov infiltration equation

An empirical model i = a·t^n describing cumulative infiltration as a power function of time. It fits early-time data well but does not predict a steady final rate.

Crop coefficient Kc

A dimensionless factor multiplying reference evapotranspiration to give crop evapotranspiration. Its value changes with crop type and growth stage, peaking at mid-season.

Penman–Monteith equation

The standard formula combining net radiation, air temperature, humidity, and wind speed to estimate reference evapotranspiration from a grass reference surface.

Hooghoudt drainage equation

Relates drain spacing to soil hydraulic conductivity, drain depth, and design discharge. It accounts for flow both above and below the drain level.

Drawbar power

Power delivered at the tractor hitch, equal to draft force multiplied by forward speed. It is always lower than engine power because of slip and rolling losses.

Stokes' law

Gives the terminal settling velocity of a small sphere in a viscous fluid as proportional to the square of its diameter. It underpins soil particle-size sedimentation analysis.

De Morgan's theorems

Boolean identities stating that the complement of a product equals the sum of complements, and the complement of a sum equals the product of complements.

Inverting amplifier gain

For an ideal op-amp, closed-loop gain equals negative feedback resistance divided by input resistance. The output is inverted relative to the input signal.

Nyquist sampling criterion

A signal must be sampled at more than twice its highest frequency component to be reconstructed without aliasing. Lower rates fold high frequencies into false low ones.

Successive-approximation ADC

A converter that tests bits from most to least significant against a reference, resolving one bit per clock. Its resolution is reference voltage divided by two to the n.

Wheatstone bridge balance

The bridge nulls when the ratio of two adjacent arms equals the ratio of the other two. At balance, no current flows through the galvanometer branch.

PID control terms

Proportional action responds to present error, integral action removes steady offset, and derivative action anticipates trend. Together they trade speed against stability.

Instrument sensitivity

The change in output per unit change in input, forming the slope of the calibration curve. High sensitivity does not by itself guarantee low measurement uncertainty.

Hysteresis

The difference in instrument output for the same input when approached from increasing versus decreasing directions. It arises from friction, backlash, or magnetic effects.

Relative humidity

The ratio of actual water vapour pressure to saturation vapour pressure at the same temperature, expressed as a percentage. It reaches 100% at the dew point.

Dew point temperature

The temperature to which moist air must be cooled at constant pressure for water vapour to begin condensing. It is always at or below the dry-bulb temperature.

Minimum roof slope

The smallest pitch that sheds rainwater reliably for a given covering. Metal sheeting typically needs about 1 in 5, while tiles require steeper pitches.

Limit state design

A structural method checking that factored load effects do not exceed design resistance. Ultimate and serviceability states are verified separately.

Water-cement ratio

The mass of water divided by mass of cement in a concrete mix. Lower ratios increase strength and durability but reduce workability.

Safe grain storage moisture

The maximum grain water content at which mould growth is prevented during storage. For cereals it is roughly 12 to 14 percent, depending on temperature.

Greenhouse ridge orientation

The direction of the greenhouse ridge line. North-south orientation balances light across both sides and favours winter light capture in most latitudes.

Cation exchange capacity

The quantity of exchangeable cations a soil can hold, expressed in cmol per kilogram. Higher values indicate greater nutrient retention and pH buffering.

Law of the minimum

Liebig's principle that growth is governed by the nutrient in shortest supply relative to need, not by the total quantity of nutrients present.

Light compensation point

The light level at which gross photosynthesis exactly balances respiration, giving zero net carbon gain. Plants cannot grow below this irradiance.

Nitrogenase inhibition

The enzyme fixing atmospheric nitrogen is irreversibly damaged by oxygen and suppressed by high soil nitrate, so legumes rely on leghaemoglobin to control oxygen.

Standard error of mean

The standard deviation of a sample divided by the square root of sample size. It measures how precisely the sample mean estimates the population mean.

Coefficient of variation

The ratio of standard deviation to mean, usually expressed as a percentage. It allows comparison of variability between datasets measured in different units.

Randomised complete block design

An experimental layout in which each treatment appears once per block, and blocks group similar plots. It controls field gradient effects and is analysed by two-way ANOVA.

Soil pH and nutrient availability

Most nutrients are most available near pH 6 to 7. Below this, aluminium and manganese become toxic; above it, iron, zinc, and phosphorus become less available.