Do not use appliances, if

Question

Examoogle · Accepted Answer

both a and b

Explanation: Operating electrical appliances with structural damage or exposed wiring poses severe safety risks, including electric shock, short circuits, and fire hazards. Insulation failure allows current to follow unintended paths, which can lead to energized metal casings or ignition of surrounding materials.

Working Principle: Electrical appliances rely on intact insulation (dielectric material) to contain current within the conductive paths. When wires are exposed or the casing is damaged, the insulation breakdown occurs, leading to leakage current ($I_L$). If the resistance to ground is low, the fault current can be high, potentially bypassing protective devices if they are not rated correctly for the specific fault.

Key Formulas: $I = \frac{V}{R}$ — Ohm's law, demonstrating that decreased resistance (due to short circuits or shorts to ground) increases fault current.; $P = I^2R$ — Joule's law, where excessive current flowing through unintended paths leads to heat generation and potential fire.

Key Points: Damaged casing can lead to chassis being energized at supply potential.; Exposed wires increase the probability of accidental contact by the user.; Always perform a visual inspection of power cords and plugs before connecting to mains.; Damaged insulation reduces the dielectric strength between conductors and ground.

Advantages: Prevents life-threatening electric shocks; Mitigates fire risks in residential and industrial environments

Applications: Electrical safety protocols; Preventive maintenance of household electronics; Industrial machinery inspection

Additional Info: Exposed wires can result in a 'phase-to-earth' fault.. Option C is incorrect because an appliance working properly is safe to use unless other defects exist.. Routine PAT (Portable Appliance Testing) is recommended for identifying these hazards in commercial environments.

Answer: D is correct — Using appliances with physical damage or exposed conductors creates an immediate risk of electrical fault, shock, or fire.

Exam Tip: When analyzing electrical safety questions, always prioritize the path of the current; if insulation is compromised, assume the safety grounding path is insufficient to protect the user.

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