Electric Welding MCQ PDF

1. Which of the following falls under the category of plastic or non-fusion welding ?

(a) Resistance welding.
(b) Electron beam welding.
(c) Electro-slag welding.
(d) Arc welding.

2. Which of the following falls under the category of fusion or non-pressure welding?

(a) Resistance welding.
(b) Metal-arc welding.
(c) Ultrasonic welding.
(d) Explosive welding.

3. Proper selection of welding depends upon, in addition to cost involved,

(a) kinds of metals to be joined.
(b) nature of products to be fabricated.
(c) production technique used.
(d) all of the above.

4. The metal surfaces for electrical resistance welding must be

(a) cleaned.
(b) lubricated.
(c) moistened.
(d) rough.

5. Resistance welding cannot be used for

(a) ferrous materials.
(b) non-ferrous materials.
(c) dielectrics.
(d) any of the above.

6. In electrical resistance welding the greatest resistance is offered by

(a) metal surface.
(b) contact layer of metals to be welded.
(c) contact point of electrode with metal top.
(d) contact point of electrode with metal bottom.

7. In electric resistance welding

(a) the current required exceeds 100 A.
(b) the voltage required ranges from 4 to 12 V.
(c) the amount of power supplied to the weld usually ranges from 60 watts to 80 watts for each square mm of area.
(d) all of the above.

8. Resistance to the flow of current is made of

(a) resistance of current path in the work.
(b) resistance between the contact surfaces of the parts being welded.
(c) resistance between the electrodes and the surface of the parts being welded.
(d) all of the above.

9. In resistance welding, the magnitude of current is controlled

(a) by varying the primary voltage of the welding transformer using an auto-transformer between supply and welding transformer.
(b) by changing the primary turns of the welding transformer.
(c) by varying the magnitude and waveform of the primary as well as secondary current by using thyratron or ignitron.
(d) any of the above.

10. The main drawback of resistance welding is

(a) high initial as well as maintenance cost.
(b) difficult shapes and sections cannot be welded.
(c) only similar metals can be welded.
(d) parent metal is affected.

11. Plain and butt welds may be used on materials up to thickness of about

(a) 5 mm
(b) 10 mm
(c) 25 mm
(d) 40 mm

12. In upset butt welding

(a) the faces of the metal pieces to be joined are prepared for even contact.
(b) heating is obtained by the contact resistance of metal pieces to be welded.
(c) the voltage required is 2 – 8 V and current required ranges from 50 A to several hundred amperes depending upon material and the area to be welded at a time.
(d) all of the above.

13. In flash-butt welding

(a) no special preparation of the faces to be welded is necessary.
(b) clean and pure weld is obtained.
(c) power requirement is less.
(d) all of the above.

13. Spot welding process basically depends on

(a) generation of heat.
(b) application of forging pressure.
(c) both (a) and (b).
(d) ohmic resistance.

14. In spot welding, composition and thickness of the base metal determines the

(a) holding time.
(b) amount of weld current.
(c) amount of squeeze pressure.
(d) all of the above.

15. The tips of the electrodes, for spot welding are made of

(a) carbon.
(b) copper alloy or pure copper.
(c) mica.
(d) porcelain.

16. The power factor of a spot welding machine is expected to be about

(a) 0.3 to 0.5 lagging.
(b) 0.8 to 0.85 lagging.
(c) 0.75 to 0.85 leading.
(d) unity.

17. During spot welding, the current flows for

(a) fraction of a minute.
(b) fraction of a second to several seconds.
(c) few milliseconds.
(d) few microseconds.

18. Spot welding is employed for

(a) thin metal sheets (thickness being usually limited to 10 – 12 mm).
(b) castings only.
(c) thick sections.
(d) rough and irregular surfaces.

19. Spot welding

(a) makes the weld air tight.
(b) makes the weld water tight.
(c) provides mechanical strength.
(d) all of the above.

20. In spot welding

(a) it is desirable to clean the sheets thoroughly before welding.
(b) the work-pieces being welded are pressed together by mechanical pressure exerted through electrodes.
(c) current required is above 5,000 A and the voltage between the electrodes is usually less than 2 V (open-circuit voltage less than 12 V).
(d) all of the above.