Electric Drives and Motors MCQ Part-6

1. Radiant heating used for_________.

a. Drying of paints and varnishes

b. Annealing of metals

c. Melting of ferrous metals

d. Any of the above

2. Direct resistance heating is used in___________.

a. Resistance welding

b. Salt-bath furnace

c. Electrode boiler

d. All of the above

3. Resistance ovens used for_________.

a. Vulcanizing and hardening of synthetic materials

b. Drying of vanish coatings, drying and baking of potteries

c. Domestic and commercial heating

d. All of the above

4. The function(s) of an heating chamber is/are to__________.

a. Confine the atmosphere around the charge

b. Store as much of the heat supplied as may be practicable and economical

c. control the cooling rate of the charge and control the distribution of heat within the chamber

d. All of  the above

 

5. For obtaining best result, the infrared lamps should be located from the object to be heated at distance of_________.

a. 10-20 cm

b. 25-30 cm

c. 40-50 cm

d. 50-60 cm

6. In direct arc furnace which of the following is of high value ?

a. Voltage

b. Current

c. Power factor

d. All of the above

7. The power factor at which  the direct arc furnace operates is_______.

a. Low leading

b. Low lagging

c. High leading

d. Unity

8. For arc heating, the electrodes used are made of________.

a. Graphite

b. Aluminium

c. Copper

d. Tungsten

9. In an arc furnace, the choke is provided to________.

a. Improve the power factor

b. Reduce the surge severity

c. Stabilize the arc

d. All of the above

10. It is desirable to operate the are furnace at a power factor of_______.

a. Zero

b. 0.707 lagging

c. 0.707 leading

d. Unity

11. It is desirable to keep the arc length short in order to_________.

a. Have better stirring action and reduce oxidation problem

b. Increase the life of roof refractory

c. have better heating

d. All of the above

 

12. The arc furnaces of conical shapes have the advantage(s) of ______.

a. Low power consumption

b. Reduced radiation losses

c. Large surface area per unit bath volume

d. All of the above

 

13. In arc furnace, energy losses that take place in the furnace are______.

a. Losses through escape gasses

b. Losses through walls

c. Losses through water cooling

d. All of the above

 

14. In submerged arc furnace the power is controlled by________.

a. Varying the spacing between the electrodes

b. Varying the voltage applied to the electrodes

c. Either (a) or (b)

d. Varying  the arc length

15. The main application of indirect arc furnace is to melt_________.

a. Steel 

b. Iron

c. Non-ferrous metals

d. None of the above

16. For power transformers employed for arc furnaces, it is desirable to arrange the furnace and the transformer in such a way that leads are_______.

a. Shorter in length and placed close together

b. Longer in length and placed close together

c. Shorter in length and placed distant apart

d. In any arrangement

17. In induction heating__________.

a. Heat is produced due to currents induced in the charge by electromagnetic action

b. Magnetic materials can be easily treated in comparison to non-magnetic materials

c. The resistance of the charge must be low and voltage applied must be high in order to produce sufficient heat

d. All of the above

 

18. Induction heating takes place in__________.

a. Conducting materials may be magnetic or non-magnetic

b. Conducting but non-magnetic materials

c. Conducting and magnetic materials

d. Insulating materials

19. Induction hardening is possible in case of___________.

a. AC supply only

b. DC supply only

c. Non-conducting materials only

d. Ferrous materials only

20. Low frequency supply is necessary for direct core type induction furnaces because__________.

a. With normal frequency supply the electromagnetic forces cause severe stirring action in the molten metal

b. Magnetic coupling between the primary and secondary circuit is poor

c. Both (a) and (b)

d. None of (a) (b)

21. In induction heating, which of the following is of high value ?

a. Current

b. Voltage

c. Frequency

d. Power factor

22. Induction furnaces are used for__________.

a. Heating of insulators

b. Heat treatment of castings

c. Melting of aluminium

d. All of the above

23. The advantage(s) of eddy current heating is/are______________.

a. Heat can be made to penetrate into metal surface to any desired depth

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

c. Easy temperature control, little wastage of heat and possibility of heating in vacuum or other special atmosphere

d. All of the above

 

24. The supply frequency usually employed for high frequency eddy current heating is____________.

a. 1 kHz

b. 5 kHz

c. 10 kHz to 400 kHz

d. 10 MHz

25. In case of core-loss induction furnace, the charge should be in ________.

a. Molten state

b. Solid state

c. Either of (a) or (b)

 

26. High frequency induction heating is used for________.

a. Non-ferrous metals only

b. Ferrous metals only

c. Both ferrous and non-ferrous metals

 

• Electric Drives and Motors MCQ Part-1
• Electric Drives and motors MCQ Part-2
• Electric Drives and Motors MCQ Part-3
• Electric Drives and Motors MCQ Part-4
• Electric Drives and Motors MCQ Part-5
• Electric Drives and Motors MCQ Part-7
• Electric Drives and Motors MCQ Part-8
• Electric Drives and Motors MCQ Part-9
• Electric Drives and Motors MCQ Part-10