Dielectric Breakdown | Ionization of Gases | Breakdown Voltage & strength - MCQ's
This sets of mcq's or objectives focuses on dielectric breakdown, primary and secondary ionization, breakdown voltage, breakdown strength, Factors affecting Breakdown Strengths of Solid, Liquid and Gaseous dielectric materials....
SET 1 of Dielectric Breakdown, Ionization of Gases, Breakdown Voltage & strength MCQ's
1. Breakdown strength decreases with increase in (i)-----& increases with increase in -----(ii).
A. i) humidity ii) electrode diameter
B. i) temperature ii) gap distance
C. A & B
D. None of these
Answer B
Marks 2
2. An electron liberated due to impact of free electron is -----------ionization & due to impact of positive ion is ------------ionization.
A. primary, secondary
B. secondary, primary
C. primary, tertiary
D. can be all
Answer A
Marks 2
3. In primary ionization, electron is liberated from --------------by --------------.
A. positive ion, gas molecule
B. free electron , gas molecule
C. gas molecule, free electron
D. gas molecule, positive ion.
Answer C
Marks 2
4. In secondary ionization, electron is liberated from --------------by -------------- .
A. positive ion, electrode surface
B. free electron , electrode surface
C. electrode surface, free electron
D. electrode surface, positive ion
Answer D
Marks 2
5. The ----------------- can be used as a raw material for making Porcelain.
A. glaze producing agents
B. clays
C. filler & fluxing agents
D. all
Answer D
Marks 2
6. Out of natural resins (i)----- is an animal resin and (ii)----- is a sticky , gummy like substance.
A. i)shellac ii)amber
B. i) amber ii) shellac
C. i)shellac ii) wood
D. i) amber ii) wood
Answer C
Marks 2
7. If the size of the impurity particle in the oil is ------ ,------- will be the breakdown strength.
A. larger, lower
B. lower, lower
C. larger, larger
D. B & C
Answer A
Marks 2
SET 2 of Dielectric Breakdown, Ionization of Gases, Breakdown Voltage & strength MCQ's
8. ----------- electrodes will have less breakdown voltage than ----------------electrode.
A. Copper, steel
B. Steel , Copper
C. Aluminium, Steel
D. A & C
Answer D
Marks 2
9. Moisture absorbed by an insulating material causes decrease in i) ----------- and increase in ii)---------- .
A. i) surface resistivity ii) dielectric constant
B. i)dielectric constant ii) tan delta
C. i) tan delta ii)conductivity
D. i)conductivity ii) surface resistivity
Answer A
Marks 2
10. Glass, porcelain & quartz are -----------class insulating material whereas cotton, rayon, silk & paper are -----------class insulating material
A. H and Y
B. E and B
C. B and C
D. C and Y
Answer D
Marks 2
11.Enamels are used to ---------- .
A. Reduce hygroscopicity
B. To increase insulation strength
C. To reduce oxidation
D. A & B
Answer D
Marks 2
12. Some materials used as enamels are
A. Polyamide & polyvinyl resins
B. Polystyrene
C. Polytetrafluorethylene (PTFE)
D. A & C
Answer D
Marks 2
13. Which of the following applications, include use of low permittivity ceramic -
1. Suspension insulators for high voltage lines
2. Super conductors
3. Pin insulators for low voltage lines
4. High voltage cables
A. 1 and 2 only
B. 1 and 3 only
C. 2 and 3 only
D. 1, 2and 3.
Answer B
Marks 2
14. The breakdown voltage of transformer oil is found to be 30kV. If the gap spacing between electrodes in the test cell is 2.5mm, the dielectric strength of transformer oil is:
A. 12 kV/mm
B. 120 kV/mm
C. 1.2 kV/mm
D. 12 kV/cm
Answer A
Marks 2
15. The dielectric strength of PVC is 40,000V/mm at 50 Hz, calculate the thickness of insulation on a wire carrying 33 kV to sustain the breakdown.
A. 0.0825 mm
B. 8.25 mm
C. 0.825mm
D. 825 mm
Answer C
Marks 2
