Final answer:
3) Both A and B, The case or housing of electrical apparatus and fencing around installations serve to prevent accidental contact with energized parts and to protect the equipment, addressing both electrical shock and physical damage concerns.
Step-by-step explanation:
The purpose of the case or housing of apparatus, or the fence or walls surrounding an installation, serves both to prevent personnel from accidentally contacting energized parts and to protect the equipment from physical damage. This dual purpose is essential for maintaining safety in electrical installations.
Electrical safety systems and devices, such as the three-wire system, grounding, and the use of ground fault interrupters (GFI) or ground fault circuit interrupters (GFCI), are designed to prevent both thermal and shock hazards. The case or housing acts similarly to a Faraday cage, enclosing the device and ensuring that electrical charges reside on the outside, thus shielding the inside from stray electrical fields and potential contact with live parts.
The purpose of the case or housing of apparatus, or the fence or walls surrounding an installation is **3) Both A and B.** These protective enclosures serve a dual function. Firstly, they prevent personnel from accidentally contacting energized parts, enhancing electrical safety for workers.
Secondly, they protect the equipment from physical damage, such as impact, environmental elements, or unauthorized access. By combining these functions, these enclosures contribute to the overall safety, reliability, and longevity of electrical installations, ensuring that both people and equipment are safeguarded from potential hazards and external factors that could compromise the integrity of the system.