Electric Welding and Heating Multiple Choice Questions and Answers PDF

Electric Welding and Heating Multiple Choice Questions and Answers PDF

1. Which of the following will happen if the thickness of the refractory wall of the furnace is increased?
(a) Heat loss through furnace wall will increase
(b) Temperature inside the furnace will fall
(c) Temperature on the outer surface of furnace walls will drop
(d) Energy consumption will increase

2. Which of the following devices is necessarily required for automatic temperature control in a furnace?
(a) Thermostat
(b) Thermocouple
(c) Auto-transformer
(d) Heating elements of variable resistance material

3. In electric press, mica is used because it is _______ conductor of heat but/and ________ conductor of electricity.
(a) bad, good
(b) bad, bad
(c) good, bad
(d) good, good

4. Resistance variation method of temperature control is done by connecting resistance elements in
(a) series
(b) parallel
(c) series-parallel connections
(d) star-delta connections
(e) all of the above ways

5. Hysteresis loss and eddy current loss are used in
(a) induction heating of the steel
(b) dielectric heating
(c) induction heating of brass
(d) resistance heating

6. In heating the ferromagnetic material by induction heating, heat is produced due to
(a) induced current flow through the charge
(b) hysteresis loss taking place below Curie temperature
(c) due to hysteresis loss as well as eddy current loss taking place in the charge
(d) none of the above factors

7. Radiant heating is used for which of the following?
(a) Annealing of metals
(b) Melting of ferrous metals
(c) Heating of liquids in electric kettle
(d) Drying of paints and varnishes

8. Heat transfer by condition will not occur when
(a) bodies are kept in the vacuum
(b) bodies are immersed in water
(c) bodies are exposed to thermal radiations
(d) temperatures of the two bodies are identical

9. A perfect black body is one that
(a) transmits all incident radiations
(b) absorbs all incident radiations
(c) reflects all incident radiations
(d) absorbs, reflects and transmits all incident radiations

10. Heat is transferred simultaneously by condition, convection, and radiation
(a) inside boiler furnaces
(b) during melting of ice
(c) through the surface of the insulated pipe carrying steam
(d) from refrigerator coils to the freezer in a refrigerator

11. The process of heat transfer during the re-entry of satellites and missiles, at very high speeds, into earth’s atmosphere is known as
(a) ablation
(b) radiation
(c) viscous dissipation
(d) irradiation

12. The temperature inside a furnace is usually measured by which of the following?
(a) Optical pyrometer
(b) Mercury thermometer
(c) Alcohol thermometer
(d) Any of the above

13. By the use of which of the following, high-frequency power supply for induction furnaces can be obtained?
(a) Coreless transformers
(b) Current transformers
(c) Motor-generator set
(d) Multi-phase transformer

14. In induction heating ______ is abnormally high.
(a) phase angle
(b) frequency
(c) current
(d) voltage

15. By which of the following methods the temperature inside arc nace can be varied?
(a) By disconnecting some of the heating elements
(b) By varying the operating voltage
(c) By varying the current through heating elements
(d) By any of the above method

16. In a resistance furnace, the atmosphere is
(a) oxidising
(b) deoxidizing
(c) reducing
(d) neutral

17. Which of the following has the highest value of thermal conductivity?
(a) Water
(b) Steam
(c) Solid ice
(d) Melting ice

18. Induction heating process is based on which of the following principles?
(a) Thermal ion release principle
(b) Nucleate heating principle
(c) Resistance heating principle
(d) Electro-magnetic induction principle

19. Which of the following insulating materials was suitable for low-temperature applications?
(a) Asbestos paper
(b) Diatomaceous earth
(c) 80 percent magnesia
(d) Cork

20. Normal circulation is usually associated with a non-dimensional number with heat transfer
(a) Prandtl number
(b) Grashoff number
(c) Poncelet number
(d) Nusselt number

21. What should be the heating elements for a furnace?
(a) lower melting point
(b) higher temperature coefficient
(c) high specific resistance
(d) all of the above

22. ________ has the highest value of thermal conductivity.
(a) Copper
(b) Aluminium
(c) Brass
(d) Steel

23. Which of the following heating methods has maximum power factor?
(a) Arc heating
(b) Dielectric heating
(c) Induction heating
(d) Resistance heating

24. the method has a leading power factor
(a) Resistance heating
(b) Dielectric heating
(c) Arc heating
(d) Induction heating

25. _______ is used for heating non-conducting materials.
(a) Eddy current heating
(b) Arc heating
(c) Induction heating
(d) Dielectric heating

26. Which of the following methods of heating is not dependent on the frequency of supply?
(a) Induction heating
(b) Dielectric heating
(c) Electric resistance heating
(d) All of the above

27. Which of the following is an advantage of heating by electricity?
(a) Quicker operation
(b) Higher efficiency
(c) Absence of flue gases
(d) All of the above

29. When a body reflects entire radiation incident on it, then it is known as
(a) white body
(b) grey body
(c) black body
(d) transparent body

30. For the transmission of heat from one body to another
(a) the 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


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