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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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Earth wire is connected to the
ground
appliance
power house
transformer
ground
Quick Summary: An Earth wire (or grounding conductor) is a low-resistance path connected directly to the general mass of the Earth. Its primary function is to provide a safe discharge path for fault currents to prevent electric shock in the event of an insulation failure.
An Earth wire (or grounding conductor) is a low-resistance path connected directly to the general mass of the Earth. Its primary function is to provide a safe discharge path for fault currents to prevent electric shock in the event of an insulation failure.
If=ReV — The fault current (If) is determined by the supply voltage (V) divided by the earth path resistance (Re).
Rtotal=Rbody∣∣Rearth — Explains why current prefers the earth wire path due to its minimal resistance.
The principle relies on Ohms Law: V=IR. When a metal enclosure becomes live due to a fault, the earth wire offers a path of significantly lower resistance than the human body. Consequently, the fault current flows through the earth wire to the ground, triggering the circuit protection device (fuse or MCB) to disconnect the power supply rapidly.
The earth wire is typically colored green or green-yellow.
It maintains the potential of the appliance chassis at zero volts relative to the ground.
A low earth electrode resistance is critical for effective fault protection.
Required by safety standards like the IS 3043:1987 in India.
Prevents dangerous voltage build-up on appliance enclosures
Ensures fast operation of protective devices during ground faults
Requires periodic maintenance of earth pits for resistivity monitoring
Installation can be expensive in rocky or dry soil conditions
Domestic wiring for metallic appliances (fridges, irons)
Industrial motor frames and electrical control panels
In India, IS 3043 specifies the code of practice for earthing.
Option B is incorrect because the appliance is the device being protected, not the destination of the fault current.
Option C and D are points in the supply network, but the final safety connection must terminate at the Earth electrode.
A is correct — The earth wire provides a low-impedance path to the general mass of the Earth to discharge fault currents safely.
Always remember: The goal of earthing is to minimize touch voltage, Vtouch=If×Rearth, ensuring the person remains safe during a short circuit.