Short answer type question

Q1. What is the maximum number of point of light, fan and socket- outlets that can be connected in one sub-circuit?

Ans. Ten.

Q2. What is the maximum load (light and fan) that can be connected in one sub-circuit?

Ans. 800 Watts.

Q3. On what basis is the number of circuits/ sub-circuits determined in house wiring installations?

Ans. The number of circuits and sub-circuits is decided on the basis of total number of point to be wired and the total load to be connected to the supply system.

Q4. Which system is used for distribution of electrical energy in a building?

Ans. Distribution board system.

Q5. Which system is used in connections of various lamps or appliances in parallel?

Ans. Loop-in –system.

Q6. Which of the following wiring system is commonly used for light/fan load in domestic and commercial buildings?

(a) Cleat wiring

                (b) Casing-capping wiring

                (c) TRS wiring

                (d) Lead sheathed wiring

                (e) PVC wiring

Ans.        (e) PVC wiring

Q7. Which wiring system is employed in mechanical workshops?

Ans. Conduit wiring system (surface or concealed).

Q8. What are that points which will be consider in selecting the wiring for a particular installation?

Ans. The main points, which are considered in selection of the type of wiring for a particular installation, are safety, durability, appearance mechanical protection, permanency, accessibility and cost (initial as well as maintenance).

Q9. What is different between wire and cable?

Ans. Single wire, may be bare or covered with insulation is called the wire while several wires stranded together is called the cable.

Q10. Why conductor is covered with insulating material?

Ans. The conductor is covered with insulating material so as to prevent leakage of current from the conductor.

Q11. What are the essential properties, which the insulation used in cable must posses?

Ans. The insulating materials used in cables must have the properties of light resistivity, high flexibility, high dielectric strength, non-inflammability, non-hygroscopicity, highly resistive to moisture, acids or alkalies and capability to withstand high rupturing voltage and high temperature without much deterioration.

Q12. Which insulation is most widely used for covering wires/cables used in internal wiring?

Ans. PVC.

Q13. Why multi-stand conductors are preferred over solid conductors?

Ans. Multi-strand conductors are preferred over solid conductors because they provide flexibility and durability.

Q14. PVC cables are most widely used in internal wiring. Why?

Ans. PVC cables are most widely used in internal wiring because PVC insulation provides better flexibility, has better insulation qualities, has no chemical effect on metal of wire and gives smaller diameter of cable.

Q15. Where are flexible cords used?

Ans. Flexible cords are used as connecting wires for such purposes as from ceiling rose to lamp holder, socket outlet to portable apparatus such as radios, fans, lamps etc.

Q16. What is meant by voltage grading of cables?

Ans. Voltage grading of cable specifies the safe voltages which the insulation of the cable can withstand.

Q17. How the size of a wire or cable is given?

Ans. The size of a wire or cable is specified giving the number of strands used and diameter of each strand or giving the area of cross-section of conductor used.

Q18. How are cable specified?

Ans. The cables are specified providing size of conductor used, type of conductor used, number of cores that cable consists of, voltages grade and type of cable.

Q19. What is meant by distribution board?

Ans. Distribution board is an assembly of parts, including one or more fuses or circuit breakers, arranged for the distribution of electrical energy to different circuits or other distribution boards known as submain distribution boards.

Q20. What is meant by a switch?

Ans. A switch is a device that is used for making or breaking the electric circuit in a convenient way.

Q21. What for ceiling rose is used?

Ans. Ceiling rose is used for connecting the pendant lamps, fans or fluorescent tubes to the installation through flexible plastic or silk covered wire.

Q22. What is meant by a fuse?

Ans. Fuse is a devices used in an electrical circuit for protecting electrical equipment against overloads and/or shor-circuits.

Q23. On what principle does the fuse operate?

Ans. The action of a fuse is based upon the heating effect of the electric current. During overloads or short circuits the fuse gets heated upto melting point due to excessive current and breaks the circuit.

Q24. What kind of protection is offered by a fuse?

Ans. The fuse provides protection against short-circuits and overloads.

Q25. What function does the fuse perform?

Ans. The function of a fuse wire is (i) to carry the normal working current safely without heating and (ii) to break the circuit when current exceeds the limiting current.