---
title: "Short note: General principles of electrical services"
subject: "Building Technology"
chapter: 12
key: "semester_6/building_technology:electrical-services-principles-short"
source: https://www.bctengineer.com/q/semester_6/building_technology/electrical-services-principles-short
site: BCT Engineering
---

# Short note: General principles of electrical services

Building Technology · Chapter 12: Other services in building

- Asked in: 2070 Chaitra (old course), 4 marks
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/building_technology/electrical-services-principles-short
- Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-12

## Question

Write a short note on the general principles of electrical services.

## Short answer

The general principles are: ensure safety via earthing and protective devices; provide adequate capacity for present and future loads; design economically with low voltage drop; ensure reliability by separate circuits; make systems accessible for maintenance; follow standards; and maintain neat appearance with concealed wiring where possible.

## Answer

Electrical services in a building supply power for lighting, ventilation, appliances, communication and lifts. The general principles are:

- **Safety:** protect people and property from shock and fire (earthing, fuses, MCB, RCD/ELCB).
- **Adequacy:** the number of points, capacity of wires and loads must be enough for present and future use.
- **Economy and simple design:** short runs, balanced loads on phases, minimum voltage drop (not more than 3-5%).
- **Reliability and continuity:** separate circuits for lighting (5 A) and power (15 A); a fault on one circuit should not stop others.
- **Accessibility:** distribution board at an accessible central location; switches at about 1.2-1.4 m height.
- **Standards:** follow the Nepal Electricity rules and standard (NBC / IS 732 / IEC); use ISI/NS marked materials.
- **Appearance and flexibility:** concealed wiring where possible; provision for extension; good lighting levels.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Which devices form part of the safety principle in electrical services?
   A. Earthing, fuses, MCB and RCD/ELCB
   B. Only decorative switches
   C. Longer wires
   D. Extra sockets per circuit
   Answer: A. Safety against shock and fire is achieved by earthing and protective devices such as fuses, MCB and RCD/ELCB. (Key point: Safety principle)

2. Which is part of economy and simple design?
   A. Long runs and unbalanced phases
   B. Voltage drop up to 15%
   C. Short runs, balanced loads on phases and voltage drop not more than 3-5%
   D. Single circuit for the whole building
   Answer: C. Short runs, balanced phase loads and low voltage drop keep the system economical and efficient. (Key point: Economy principle)

3. Where should the distribution board and switches be placed?
   A. DB at an accessible central location; switches at about 1.2-1.4 m height
   B. DB inside a locked ceiling void; switches at 3 m
   C. DB in the bathroom; switches at floor level
   D. DB on the roof; switches at 0.3 m
   Answer: A. The DB should be centrally accessible and switches at about 1.2-1.4 m. (Key point: Accessibility)

4. What does the principle of adequacy require?
   A. Points and wire capacity enough for present and future loads
   B. Only the minimum points now
   C. Oversized wires with no points
   D. Capacity for present load only
   Answer: A. Adequacy means the number of points, wire capacity and loads are sufficient for present and future use. (Key point: Adequacy)

## Related in Building Technology

- [Electrical services principles, wiring, safety](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aelectrical-principles-wiring-safety) — Building Technology, chapter 12

## Related in other subjects

- [General electrical rules for installation and wiring](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Aelectrical-rules-installation) — Industrial Power Distribution and Illumination, chapter 1, asked 3×