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The earth wire should be
Good conductor of electricity
Mechanical strong
Both (a) and (b)
Mechanical is strong but bad conductor of electricity
Both (a) and (b)
An earth wire serves as a safety path for fault currents to flow into the ground during electrical leakage. To perform this function effectively, it must have minimal electrical resistance and high mechanical integrity to withstand physical stress and environmental conditions.
An earth wire serves as a safety path for fault currents to flow into the ground during electrical leakage. To perform this function effectively, it must have minimal electrical resistance and high mechanical integrity to withstand physical stress and environmental conditions.
R=╧БALтАЛ тАФ Relation showing resistance depends on material resistivity and cross-section
IfaultтАЛ=ReтАЛ+RgтАЛVтАЛ тАФ Fault current flow through the earthing system where ReтАЛ is earth wire resistance
The earth wire creates a low-impedance path (Z=R+jX) connected to the metallic body of electrical equipment. When an insulation failure occurs, the fault current flows through the earth wire rather than the user's body, as it offers the path of least resistance (IfaultтАЛ=ZearthтАЛVтАЛ). The mechanical strength ensures the continuity of this safety path against vibrations, corrosion, and physical damage.
The earth wire must ensure a low impedance path to trigger protection devices (like MCBs/ELCBs) during a fault.
Mechanical strength is crucial to prevent the conductor from snapping, which would leave the equipment chassis live.
Common materials include Galvanized Iron (GI) or Copper, chosen for conductivity and corrosion resistance.
Earthing prevents the buildup of dangerous static charges on metallic components.
Prevents electric shock to users during insulation failure.
Protects equipment from voltage surges and transients.
Provides a stable reference potential (zero voltage reference).
High maintenance required for earth electrodes (moisture content).
Prone to corrosion if not properly treated or protected.
Domestic wiring grounding.
Industrial machinery safety bonding.
Substation lightning protection systems.
The earth resistance for a large power station should be less than 0.5 ohms.
Option D is contradictory because a safety grounding device must be highly conductive; a 'bad conductor' would increase fault impedance, failing to trip protective breakers.
C is correct тАФ An effective earth wire must maintain a low-resistance path for fault current and possess enough mechanical strength to ensure physical continuity.
Always remember that in fault analysis, the earth wire resistance is assumed to be negligible compared to the fault impedance to maximize current for protective relay tripping.