In this article, we shared the electrical heating objective questions and answers for electrical and electronics engineers.
Electrical Heating Objective Questions
The below list provides all the multiple-choice questions related to electrical heating.
Answers are available at the bottom of the article.
1. Which of the following methods is used to control the temperature in resistance furnaces?
| A) | Variation of resistance |
| B) | Variation of voltage |
| C) | All of these answers |
| D) | Periodical switching on and off of the supply |
2. ____ has the highest value of thermal conductivity.
| A) | Aluminium |
| B) | Copper |
| C) | Brass |
| D) | Steel |
3. When a body reflects the entire radiation incident on it, then it is known as
| A) | grey body |
| B) | white body |
| C) | black body |
| D) | transparent body |
4. In the indirect resistance heating method, maximum heat transfer takes place by
| A) | conduction |
| B) | radiation |
| C) | any of these answers |
| D) | convection |
5. Radiations from proportional to a black body are
| A) | T |
| B) | T2 |
| C) | T3 |
| D) | T4 |
6. Which of the following methods of heating is not dependent on the frequency of supply?
| A) | Dielectric heating |
| B) | Induction heating |
| C) | All of these answers |
| D) | Electric resistance heating |
7. For intermittent work which of the following furnaces is suitable?
| A) | None of these answers |
| B) | Either Electrical Welding or Electrical Welding |
| C) | Electrical Welding |
| D) | Electrical Welding |
8. In heating the ferromagnetic material by induction heating, heat is produced due to
| A) | induced current flow through the charge |
| B) | due to hysteresis loss as well as eddy current loss taking place in the charge |
| C) | none of these answers |
| D) | hysteresis loss taking place below curie temperature |
9. ____ is used for heating non-conducting materials.
| A) | Arc heating |
| B) | Induction heating |
| C) | Eddy current heating |
| D) | Dielectric heating |
10. In direct arc furnace, which of the following has high value?
| A) | Voltage |
| B) | Power factor |
| C) | All of these answers |
| D) | Current |
11. Heat transfer by the condition will not occur when
| A) | bodies are kept in a vacuum |
| B) | bodies are exposed to thermal radiations |
| C) | bodies are immersed in water |
| D) | temperatures of the two bodies are identical |
12. Hysteresis loss and eddy current loss are used in
| A) | resistance heating |
| B) | induction heating of steel |
| C) | induction heating of brass |
| D) | dielectric heating |
13. The temperature inside a furnace is usually measured by which of the following?
| A) | Mercury thermometer |
| B) | Any of these answers |
| C) | Alcohol thermometer |
| D) | Optical pyrometer |
14. In resistance heating, highest working temperature is obtained from heating elements made of ____
| A) | nichrome |
| B) | silver |
| C) | nickel copper |
| D) | silicon carbide |
15. Radiant heating is used for which of the following?
| A) | Heating of liquids in an electric kettle |
| B) | Melting of ferrous metals |
| C) | Annealing of metals |
| D) | Drying of paints and varnishes |
16. ____ method has a leading power factor
| A) | Resistance heating |
| B) | Arc heating |
| C) | Dielectric heating |
| D) | Induction heating |
17. In a domestic cake baking oven the temperature is controlled by
| A) | series-parallel operation |
| B) | thermostat |
| C) | voltage variation |
| D) | auto-transformer |
18. By the use of which of the following, high-frequency power supply for induction furnaces can be obtained?
| A) | Coreless transformers |
| B) | Motor-generator set |
| C) | Multi-phase transformer |
| D) | Current transformers |
19. Induction furnaces are employed for which of the following?
| A) | Heating of insulators |
| B) | Heat treatment of castings |
| C) | None of these answers |
| D) | Melting aluminium |
20. 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 |
21. By which of the following methods the temperature inside a resistance furnace can be varied?
| A) | By disconnecting some of the heating elements |
| B) | By varying the current through heating elements |
| C) | By varying the operating voltage |
| D) | any of these answers |
22. For radiant heating around 2250°C, the heating elements are made of
| A) | tungsten alloy |
| B) | copper alloy |
| C) | stainless steel alloy |
| D) | carbon |
23. The material of the heating element for a furnace should have
| A) | all of these answers |
| B) | higher temperature co-efficient |
| C) | lower melting point |
| D) | high specific resistance |
24. 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 |
25. For heating element high resistivity material is chosen to
| A) | reduce the effect of oxidation |
| B) | increase the life of the heating element |
| C) | produce large amount of heat |
| D) | reduce the length of heating element |
26. Property of low-temperature co-efficient of the heating element is desired due to which of the following reasons?
| A) | To avoid change in kW rating with temperature |
| B) | Both To avoid initial rush of current and To avoid change in kW rating with temperature |
| C) | To avoid initial rush of current |
| D) | Either To avoid initial rush of current or To avoid change in kW rating with temperature |
27. In an electric room heat convector the method of heating used is
| A) | arc heating |
| B) | resistance heating |
| C) | induction heating |
| D) | dielectric heating |
28. In arc furnace, the function of the choke is
| A) | none of these answers |
| B) | to stabilize the arc |
| C) | to reduce severity of the surge |
| D) | to improve power factor |
29. Which of the following insulating materials is suitable for low-temperature applications?
| A) | Asbestos paper |
| B) | Cork |
| C) | 80 percent magnesia |
| D) | Diatomaceous earth |
30. Induction heating takes place in which of the following?
| A) | Conducting materials which may or may not be magnetic |
| B) | Insulating materials |
| C) | Conducting materials which are magnetic |
| D) | Conducting materials which are non-magnetic |
31. Heat is transferred simultaneously by condition, convection, and radiation
| A) | inside boiler furnaces |
| B) | through the surface of the insulted pipe carrying steam |
| C) | from refrigerator coils to freezer of a refrigerator |
| D) | during melting of ice |
32. The electrode of a direct arc furnace is made of
| A) | silver |
| B) | tungsten |
| C) | copper |
| D) | graphite |
33. In a resistance furnace the atmosphere is ____
| A) | deoxidising |
| B) | reducing |
| C) | neutral |
| D) | oxidising |
34. A perfect black body is one that
| A) | transmits all incident radiations |
| B) | reflects all incident radiations |
| C) | absorbs, reflects and transmits all incident radiations |
| D) | absorbs all incident radiations |
35. Which of the following is an advantage of eddy current heating?
| A) | Heat at very high rate can be generated |
| B) | The amount of heat generated can be controlled accurately |
| C) | The area of the surface over which heat is produced can be accurately controlled |
| D) | All of these answers |
36. For the transmission of heat from one body to another
| A) | both bodies must be solids |
| B) | at least one of the bodies must have some source of heating |
| C) | the temperature of the two bodies must be different |
| D) | both bodies must be in contact |
37. Which of the following heating methods has maximum power factor?
| A) | Resistance heating |
| B) | Dielectric heating |
| C) | Arc heating |
| D) | Induction heating |
38. In induction heating ____ is abnormally high.
| A) | current |
| B) | phase angle |
| C) | frequency |
| D) | voltage |
39. Resistance variation method of temperature control is done by connecting resistance elements in
| A) | series |
| B) | parallel |
| C) | all of these answers |
| D) | series-parallel connections |
| E) | star-delta connections |
40. Direct arc furnaces have which of the following power factors?
| A) | Low, lagging |
| B) | Any of these answers |
| C) | Unity |
| D) | Low, leading |
41. Due to which of the following reasons it is desirable to have short arc length ?
| A) | To achieve better heating |
| B) | To increase the life of roof refractory |
| C) | To reduce problem of oxidation |
| D) | All of these answers |
| E) | To have better stirring action |
42. Which of the following has the highest value of thermal conductivity?
| A) | Steam |
| B) | Melting ice |
| C) | Solid ice |
| D) | Water |
43. Ajax Wyatt furnace is started when
| A) | it is fully empty |
| B) | it is filled below core level |
| C) | it is filled above core level |
| D) | none of these answers |
44. A non-dimensional number generally associated with natural convection heat transfer is
| A) | Nusselt number |
| B) | Grashoff number |
| C) | Prandtl number |
| D) | Pecekt number |
45. The process of heat transfer during the re-entry of satellites and missiles, at very high speeds, into earths atmosphere is known as
| A) | radiation |
| B) | irradiation |
| C) | ablation |
| D) | viscous dissipation |
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