Earthing of electrical equipment is necessary for the protection against

Question

Examoogle · Accepted Answer

Option C: Danger of electric shock

Explanation & Concepts:
Earthing provides a low-impedance path to the ground for fault currents in the event of an insulation failure. This ensures that the potential of the metal enclosure remains at zero volts relative to the ground, preventing dangerous electric shocks to human operators.

Working Principle: When a phase conductor comes into contact with the metallic enclosure of an appliance due to insulation breakdown, the enclosure becomes energized. By connecting the enclosure to the earth via a low-resistance path, a large fault current ($I_f = V_{phase} / Z_{loop}$) flows through the ground wire, causing the protection device (MCB/fuse) to trip immediately, thereby isolating the circuit and eliminating the shock hazard.

Key Formulas: $I_f = \frac{V}{R_e + R_s}$ — where $I_f$ is the fault current, $V$ is supply voltage, $R_e$ is earth resistance, and $R_s$ is source/line resistance.

Key Points: Earthing ensures the potential of non-current carrying metallic parts remains at ground potential.; It triggers protective devices like fuses or circuit breakers during a short circuit to earth.; Protects equipment from lightning surges and static electricity build-up.; Essential for stable reference voltage in electronic circuits.

Advantages: Prevents fatal electric shocks; Provides surge protection against overvoltages; Maintains a stable potential reference

Disadvantages: Requires regular maintenance to ensure low resistance; Performance depends on soil resistivity

Applications: Domestic wiring (3-pin sockets); Industrial machinery grounding; Power transformer neutral grounding

Additional Info: Option A is protected by Overload Relays or Fuses.. Option B is managed by Voltage Stabilizers or Surge Protectors.. Option D is protected by Thermal Relays or proper conductor sizing.

Answer: C is correct — Earthing is primarily employed to shunt leakage current to the ground, thereby preventing the metal chassis of an electrical device from reaching a dangerous potential relative to earth.

Exam Tip: Always remember: Overload protection is for the device (using Fuses/MCBs), while Earthing is for the user (protecting against electric shock).

Examoogle · Answer

Option A: Overloading

Examoogle · Answer

Option B: Voltage fluctuation

Examoogle · Answer

Option D: High conductor temperature

Correct Answer

Discussion (0)

Correct Answer

Related Questions

Discussion (0)