Earth wire is connected to the

Question

Examoogle · Accepted Answer

ground

Explanation: 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.

Working Principle: 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.

Key Formulas: $I_{f} = \frac{V}{R_{e}}$ — The fault current ($I_f$) is determined by the supply voltage ($V$) divided by the earth path resistance ($R_e$).; $R_{total} = R_{body} || R_{earth}$ — Explains why current prefers the earth wire path due to its minimal resistance.

Key Points: 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.

Advantages: Prevents dangerous voltage build-up on appliance enclosures; Ensures fast operation of protective devices during ground faults

Disadvantages: Requires periodic maintenance of earth pits for resistivity monitoring; Installation can be expensive in rocky or dry soil conditions

Applications: Domestic wiring for metallic appliances (fridges, irons); Industrial motor frames and electrical control panels

Additional Info: 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.

Answer: A is correct — The earth wire provides a low-impedance path to the general mass of the Earth to discharge fault currents safely.

Exam Tip: Always remember: The goal of earthing is to minimize touch voltage, $V_{touch} = I_f 	imes R_{earth}$, ensuring the person remains safe during a short circuit.

Related Questions

Discussion (0)