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Moisture content in the soil _______ the earth soil resistance
Increase
Decrease
Does not affect
None of the above
Decrease
The earth soil resistance decreases as moisture content increases because water acts as an electrolytic solution when mixed with soil salts, thereby improving conductivity. Dry soil is essentially an insulator with very high resistance, whereas moisture provides the ions necessary for current flow.
The earth soil resistance decreases as moisture content increases because water acts as an electrolytic solution when mixed with soil salts, thereby improving conductivity. Dry soil is essentially an insulator with very high resistance, whereas moisture provides the ions necessary for current flow.
R=A╧БLтАЛ тАФ where ╧Б is the soil resistivity, L is length, and A is the area of the electrode contact
╧БтИЭM1тАЛ тАФ where M is the moisture content
The electrical conductivity of soil is primarily determined by the moisture content and the concentration of dissolved minerals (salts). Water lowers the contact resistance between soil particles and the grounding electrode by filling air voids, creating a conductive bridge that significantly reduces the total ohmic resistance of the grounding system.
Dry soil has extremely high resistivity, making it unsuitable for grounding.
Moisture content is the most significant factor affecting soil resistivity.
Dissolved salts in water further decrease resistance by increasing ion mobility.
Excessive water can sometimes lead to instability, but for grounding purposes, higher moisture is preferred.
Grounding electrodes are often treated with chemicals (like salt or bentonite) to retain moisture and improve conductivity.
Lower ground resistance improves safety by providing a low-impedance path for fault currents.
Ensures effective operation of lightning protection systems.
High moisture levels can accelerate the corrosion of buried metallic electrodes.
Seasonal variation in moisture can lead to inconsistent ground resistance over time.
Earthing systems for power sub-stations.
Lightning protection systems for buildings.
Grounding for communication and sensitive electronic equipment.
For most soil types, moisture content below 15-20% causes resistivity to increase sharply.
Option A is incorrect because resistance is inversely proportional to conductivity, which moisture increases.
B is correct тАФ An increase in moisture content enhances the ionic conductivity of the soil, thereby reducing the earth soil resistance.
In competitive exams, remember that soil resistivity is inversely proportional to both moisture content and salt content; always prioritize moisture-retaining additives for improving poor earthing conditions.