Fuses Interview Questions and Answers:

1. What is meant by a fuse ?

Ans. Fuse is a device used in an electrical circuit for protecting electrical equipment’s against overloads and/or short circuits.

2. 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 up to melting point due to excessive current and breaks the circuit.

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

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

4. 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.

5. Give the names of five materials with their melting points which are used for fuse element.

Ans. The materials commonly used for fuse elements are silver, tin, lead, copper and aluminium. Their melting points are 980° C, 240°C, 328°C, 1,090° C and 665° C respectively.

6. What material is mostly used for an ordinary fuse wire ?

Ans. Copper or lead-tin alloy.

7. What is fuse link ?

Ans. Fuse link is that part of the fuse which needs replacement when the fuse blows out.

8. On what factors does the current carrying capacity of a fuse depend ?

Ans. The current carrying capacity of a fuse depends upon the permissible temperature rise of the contacts of the fuse holder, size of fuse wire, fuse material and the surrounding of the fuse.

9. On what factors does the fusing current depend ?

Ans. The fusing current depends upon (i) diameter of wire (ii) length of wire (iii) fuse material (iv) x-sectional area (round or rectangular) (v) size and location of terminals (vi) type of enclosure used (vii) type of surface etc.

10. What are the purposes of using quartz sand as filler material in the construction of HRC fuse ?

Ans. The purposes of using quartz sand as filler material in the construction of HRC fuse are to absorb heat at a very high rate, to produce a substance of high resistance and avoid the oxidation of silver element.

11. What is meant by discrimination ?

Ans. Discrimination means the breaking of the faulty section of the line to an extent restricted to minimum; healthy sections of the circuit remaining in operation.

12. Can the HRC fuse be used for both ac and dc circuits. If so under what condition ?

Ans. In general an HRC fuse meant for ac circuit may not be used for dc circuits; but however, a fuse satisfying the requirement of are voltage can be used on both ac and de circuits.

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