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heating and welding MCQs

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

heating and welding Mcqs
1. The process of heat transfer during the reentry of satellites and missiles, at very high speeds, into earths atmosphere is known as_______________?
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A. radiation

B. viscous dissipation

C. ablation

D. irradiation

2. By the use of which of the following, high frequency power supply for induction furnaces can be obtained ?
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A. Current transformers

B. Coreless transformers

C. Multi-phase transformer

D. Motor-generator set
3. For the transmission of heat from one body to another__________?
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A. temperature of the two bodies must be different

B. both bodies must be solids

C. both bodies must be in contact

D. at least one of the bodies must have some source of heating

4. When a body reflects entire radiation incident on it, then it is known as____________?
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A. grey body

B. black body

C. white body

D. transparent body

5. Ajax Wyatt furnace is started when____________?
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A. it is filled above core level

B. it is fully empty

C. it is filled below core level

D. none of the above

6. _________ has the highest value of thermal conductivity?
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A. Brass

B. Copper

C. Steel

D. Aluminium

7. Resistance variation method of temperature control is done by connecting resistance elements in_____________?
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A. series

B. parallel

C. series-parallel connections

D. all of the above ways

E. star-delta connections

8. The material of the heating element for a furnace should have___________?
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A. lower melting point

B. high specific resistance

C. all of the above

D. higher temperature coefficient

9. In heating the ferromagnetic material by induction heating, heat is produced due to_____________?
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A. induced current flow through the charge

B. none of the above factors

C. hysteresis loss taking place below curie temperature

D. due to hysteresis loss as well as eddy current loss takingplace in the charge
10. For radiant heating around 2250C, the heating elements are made of____________?
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A. copper alloy

B. carbon

C. stainless steel alloy

D. tungsten alloy
11. Which of the following is an advantage of heating by electricity ?
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A. All of the above

B. Higher efficiency

C. Absence of flue gases

D. Quicker operation

12. Which of the following is an advantage of eddy current heating ?
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A. Heat at very high rate can be gene-rated

B. All of the above

C. The amount of heat generated can be controlled accurately

D. The area of the surface over which heat is produced can be accurately controlled

13. Which of the following will happen if the thickness of refractory wall of furnace is increased ?
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A. Heat loss through furnace wall will increase

B. Energy consumption will increase

C. Temperature on the outer surface of furnace walls will drop

D. Temperature inside the furnace will fall

14. Hysteresis loss and eddy current loss are used in____________?
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A. resistance heating

B. induction heating of brass

C. induction heating of steel

D. dielectric heating

15. Which of the following methods of heating is not dependent on the frequency of supply ?
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A. Induction heating

B. All of the above

C. Dielectric heating

D. Electric resistance heating
16. Which of the following heating methods has maximum power factor ?
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A. Arc heating

B. Resistance heating

C. Induction heating

D. Dielectric heating

17. In direct arc furnace, which of the following has high value ?
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A. Power factor

B. All of the above

C. Voltage

D. Current
18. In an electric room heat convector the method of heating used is______________?
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A. induction heating

B. dielectric heating

C. resistance heating

D. arc heating

19. In resistance heating highest working temperature is obtained from heating elements made of_____________?
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A. silicon carbide

B. nickel copper

C. silver

D. nichrome

20. A non-dimensional number generally associated with natural convection heat transfer is____________?
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A. Prandtl number

B. Pecelet number

C. Grashoff number

D. Nusselt number

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

41. For intermittent work which of the following furnaces is suitable ?
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A. Either of the above

B. None of the above

C. Core less furnace

D. Indirect arc furnace

42. Induction heating process is based on which of the following principles ?
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A. Nucleate heating principle

B. Electro-magnetic induction principle

C. Thermal ion release principle

D. Resistance heating principle

43. Induction heating takes place it which of the following ?
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A. Conducting materials which are magnetic

B. Conducting materials which are non-magnetic

C. Conducting materials which may or may not be magnetic

D. Insulating materials

44. The electrode of a direct arc furnace is made of____________?
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A. graphite

B. copper

C. tungsten

D. silver

45. Radiations from a black body are proportional to____________?
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A. T2

B. T1

C. T*

D. T3

46. Heat transfer by condition will not occur when____________?
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A. temperatures of the two bodies are identical

B. bodies are kept in vacuum

C. bodies are exposed to thermal radiations

D. bodies are immersed in water

47. In arc furnace the function of choke is______________?
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A. to imprpve, power factor

B. none of the above

C. to reduce severity of the surge

D. to stabilize the arc
48. method has leading power factor____________?
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A. Dielectric heating

B. Arc heating

C. Induction heating

D. Resistance heating

49. Due to which of the following reasons it is desirable to have short arc length ?
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A. To increase the life of roof refractory

B. To have better stirring action

C. To achieve better heating

D. All of the above

E. To reduce problem of oxidation

50. Which of the following insulating materials was suitable for low temperature applications ?
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A. Cork

B. Diatomaceous earth

C. Asbestos paper

D. 80 percent magnesia