Quiz  /  Heating and Welding Electrical Engineering MCQ Interview Questions and Answers PDF

  • 1. 
    Which of the following is an advantage of heating by electricity ?

  • Quicker operation
  • Higher efficiency
  • Absence of flue gases
  • All of the above

  • 2. 
    ________ has the highest value of thermal conductivity.

  • Copper
  • Aluminium
  • Brass
  • Steel

  • 3. 
    Which of the following heating methods has maximum power factor ?

  • Arc heating
  • Dielectric heating
  • Induction heating
  • Resistance heating

  • 4. 
    method has leading power factor

  • Resistance heating
  • Dielectric heating
  • Arc heating
  • Induction heating

  • 5. 
    is used for heating non-conducting materials.

  • Eddy current heating
  • Arc heating
  • Induction heating
  • Dielectric heating

  • 6. 
    Which of the following methods of heating is not dependent on the frequency of supply ?

  • Induction heating
  • Dielectric heating
  • Electric resistance heating
  • All of the above

  • 7. 
    When a body reflects entire radiation incident on it, then it is known as

  • white body
  • grey body
  • black body
  • transparent body

  • 8. 
    For the transmission of heat from one body to another

  • temperature of the two bodies must be different
  • both bodies must be solids
  • both bodies must be in contact
  • at least one of the bodies must have some source of heating

  • 9. 
    Heat transfer by condition will not occur when

  • bodies are kept in vacuum
  • bodies are immersed in water
  • bodies are exposed to thermal radiations
  • temperatures of the two bodies are identical

  • 10. 
    A perfect black body is one that

  • transmits all incident radiations
  • absorbs all incident radiations
  • reflects all incident radiations
  • absorbs, reflects and transmits all incident radiations

  • 11. 
    Heat is transferred simultaneously by condition, convection and radiation

  • inside boiler furnaces
  • during melting of ice
  • through the surface of the insulted pipe carrying steam
  • from refrigerator coils to freezer of a refrigerator

  • 12. 
    The process of heat transfer during the reentry of satellites and missiles, at very high speeds, into earth’s atmosphere is known as

  • ablation
  • radiation
  • viscous dissipation
  • irradiation

  • 13. 
    Which of the following has the highest value of thermal conductivity ?

  • Water
  • Steam
  • Solid ice
  • Melting ice

  • 14. 
    Induction heating process is based on which of the following principles ?

  • Thermal ion release principle
  • Nucleate heating principle
  • Resistance heating principle
  • Electro-magnetic induction princi¬ple

  • 15. 
    Which of the following insulating materials was suitable for low temperature applications ?

  • Asbestos paper
  • Diatomaceous earth
  • 80 percent magnesia
  • Cork

  • 16. 
    A non-dimensional number generally associated with natural convection heat transfer is

  • Grashoff number
  • Nusselt number
  • Weber number
  • Prandtl number
  • Reynold number.

  • 17. 
    The temperature inside a furnace is usually measured by which of the following ?

  • Optical pyrometer
  • Mercury thermometer
  • Alcohol thermometer
  • Any of the above

  • 18. 
    Which of the following will happen if the thickness of refractory wall of furnace is increased ?

  • Heat loss through furnace wall will increase
  • Temperature inside the furnace will fall
  • Temperature on the outer surface of furnace walls will drop
  • Energy consumption will increase

  • 19. 
    The material of the heating element for a furnace should have

  • lower melting point
  • higher temperature coefficient
  • high specific resistance
  • all of the above

  • 20. 
    In a resistance furnace the atmosphere is

  • oxidizing
  • deoxidising
  • reducing
  • neutral

  • 21. 
    By which of the following methods the temperature inside arc nace can be varied ?

  • By disconnecting some of the heating elements
  • By varying the operating voltage
  • By varying the current through heating elements
  • By any of the above method

  • 22. 
    In induction heating ______ is abnormally high.

  • phase angle
  • frequency
  • current
  • voltage

  • 23. 
    By the use of which of the following, high frequency power supply for induction furnaces can be obtained ?

  • Coreless transformers
  • Current transformers
  • Motor-generator set
  • Multi-phase transformer

  • 24. 
    Induction furnaces are employed for which of the following ?

  • Heat treatment of castings
  • Heating of insulators
  • Melting aluminium
  • None of the above

  • 25. 
    In an electric room heat convector the method of heating used is

  • arc heating
  • resistance heating
  • induction heating
  • dielectric heating

  • 26. 
    In a domestic cake baking oven the temperature is controlled by

  • voltage variation
  • thermostat
  • auto-transformer
  • series-parallel operation

  • 27. 
    In an electric press mica is used

  • as an insulator
  • as a device for power factor improvement
  • for dielectric heating
  • for induction heating

  • 28. 
    Induction heating takes place it which of the following ?

  • Insulating materials
  • Conducting materials which are magnetic
  • Conducting materials which are non-magnetic
  • Conducting materials which may or may not be magnetic

  • 29. 
    For heating element high resistivity material is chosen to

  • reduce the length of heating element
  • increase the life of the heating element
  • reduce the effect of oxidation
  • produce large amount of heat

  • 30. 
    In resistance heating highest working temperature is obtained from heating elements made of

  • nickel copper
  • nichrome
  • silicon carbide
  • silver

  • 31. 
    For intermittent work which of the following furnaces is suitable ?

  • Indirect arc furnace
  • Core less furnace
  • Either of the above
  • None of the above

  • 32. 
    Due to which of the following reasons it is desirable to have short arc length ?

  • To achieve better heating
  • To increase the life of roof refractory
  • To have better stirring action
  • To reduce problem of oxidation
  • All of the above

  • 33. 
    In the indirect resistance heating method, maximum heat-transfer takes place by

  • radiation
  • convection
  • conduction
  • any of the above

  • 34. 
    Properly of low temperature co-eflficient of heating element is desired due to which of the following reasons ?

  • To avoid initial rush of current
  • To avoid change in kW rating with temperature
  • Both (a) and (b)
  • Either (a) or (b)

  • 35. 
    Which of the following methods is used to control temperature in resistance furnaces ?

  • Variation of resistance
  • Variation of voltage
  • Periodical switching on and off of the supply
  • All of the above methods

  • 36. 
    It is desirable to operate the arc furnaces at power factor of

  • zero
  • 0.707 lagging
  • unity
  • 0.707 leading

  • 37. 
    Radiations from a black body are proportional to

  • T1
  • T2
  • T3
  • T*

  • 38. 
    In arc furnace the function of choke is

  • to stabilize the arc
  • to imprpve, power factor
  • to reduce severity of the surge
  • none of the above

  • 39. 
    Ajax Wyatt furnace is started when

  • it is filled below core level
  • it is filled above core level
  • it is fully empty
  • none of the above

  • 40. 
    In electric press, mica is used because it is _______ conductor of heat but/and    ________ conductor of electricity.

  • bad, good
  • bad, bad
  • good, bad
  • good, good

  • 41. 
    Resistance variation method of temperature control is done by connecting resistance elements in

  • series
  • parallel
  • series-parallel connections
  • star-delta connections
  • all of the above ways

  • 42. 
    Hysteresis loss and eddy current loss are used in

  • induction heating of steel
  • dielectric heating
  • induction heating of brass
  • resistance heating

  • 43. 
    In heating the ferromagnetic material by induction heating, heat is produced due to

  • induced current flow through the charge
  • hysteresis loss taking place below curie temperature
  • due to hysteresis loss as well as eddy current loss takingplace in the charge
  • none of the above factors

  • 44. 
    Radiant heating is used for which of the following ?

  • Annealing of metals
  • Melting of ferrous metals
  • Heating of liquids in electric kettle
  • Drying of paints and varnishes

  • 45. 
    Which of the following devices is necessarily required for automatic temperature control in a furnace ?

  • Thermostat
  • Thermocouple
  • Auto-transformer
  • Heating elements of variable resis-tance material

  • 46. 
    For radiant heating around 2250°C, the heating elements are made of

  • copper alloy
  • carbon
  • tungsten alloy
  • stainless steel alloy

  • 47. 
    Which of the following is an advantage of eddy current heating ?

  • The amount of heat generated can be controlled accurately
  • Heat at very high rate can be gene-rated
  • The area of the surface over which heat is produced can be accurately controlled
  • All of the above

  • 48. 
    The electrode of a direct arc furnace is made of

  • tungsten
  • graphite
  • silver
  • copper

  • 49. 
    Direct arc furnaces have which of the following power factors ?

  • Unity
  • Low, lagging
  • Low, leading
  • Any of the above

  • 50. 
    In direct arc furnace, which of the following has high value ?

  • Current
  • Voltage
  • Power factor
  • All of the above
Report Question
warning
access_time
  Time