heating and welding MCQs – Page 2

Practise focused heating and welding questions with marked answers for exam preparation and subject revision.

heating and welding Mcqs

21. The temperature inside a furnace is usually measured by which of the following ?
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A. Optical pyrometer

B. Any of the above

C. Mercury thermometer

D. Alcohol thermometer

22. Direct arc furnaces have which of the following power factors ?
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A. Unity

B. Low, leading

C. Low, lagging

D. Any of the above

23. In an electric press mica is used_____________?
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A. as an insulator

B. as a device for power factor improvement

C. for induction heating

D. for dielectric heating

24. Properly of low temperature co-eflficient of heating element is desired due to which of the following reasons ?
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A. To avoid initial rush of current

B. To avoid change in kW rating with temperature

C. Both (A) and (B)

D. Either (A) or (B)

25. Which of the following methods is used to control temperature in resistance furnaces ?
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A. Periodical switching on and off of the supply

B. Variation of voltage

C. All of the above methods

D. Variation of resistance

26. Induction furnaces are employed for which of the following ?
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A. Melting aluminium

B. Heat treatment of castings

C. Heating of insulators

D. None of the above

27. In the indirect resistance heating method, maximum heat-transfer takes place by____________?
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A. conduction</strong>

B. any of the above

C. radiation

D. convection

28. For heating element high resistivity material is chosen to______________?
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A. increase the life of the heating element

B. reduce the effect of oxidation

C. reduce the length of heating element

D. produce large amount of heat

29. Which of the following has the highest value of thermal conductivity ?
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A. Melting ice

B. Water

C. Sold ice

D. Steam

30. By which of the following methods the temperature inside arc nace can be varied ?
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A. By any of the above method

B. By varying the current through heating elements

C. By disconnecting some of the heating elements

D. By varying the operating voltage

31. It is desirable to operate the arc furnaces at power factor of_____________?
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A. zero

B. 0.707 leading

C. unity

D. 0.707 lagging

32. In a domestic cake baking oven the temperature is controlled by________________?
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A. voltage variation

B. auto-transformer

C. series-parallel operation

D. thermostat

33. In a resistance furnace the atmosphere is_____________?
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A. deoxidising

B. reducing

C. neutral

D. oxidizing

34. Heat is transferred simultaneously by condition, convection and radiation_____________?
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A. inside boiler furnaces

B. from refrigerator coils to freezer of a refrigerator

C. through the surface of the insulted pipe carrying steam

D. during melting of ice

35. In electric press, mica is used because it is _________ conductor of heat but/and __________ conductor of electricity?
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A. good, good

B. bad, good

C. good, bad

D. bad, bad

36. is used for heating non-conducting materials?
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A. Induction heating

B. Arc heating

C. Dielectric heating

D. Eddy current heating

37. In induction heating ___________ is abnormally high?
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A. phase angle

B. current

C. voltage

D. frequency

38. A perfect black body is one that_____________?
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A. absorbs all incident radiations

B. transmits all incident radiations

C. reflects all incident radiations

D. absorbs, reflects and transmits all incident radiations

39. Radiant heating is used for which of the following ?
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A. Annealing of metals

B. Drying of paints and varnishes

C. Heating of liquids in electric kettle

D. Melting of ferrous metals

40. Which of the following devices is necessarily required for automatic temperature control in a furnace ?
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A. Thermostat

B. Heating elements of variable resis-tance material

C. Thermocouple

D. Auto-transformer

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