MCQOPTIONS
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MCQOPTIONS
This section includes 66 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering Questions knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Which theory explains the mechanism for breakdown under different conditions? |
| A. | Townsend theory |
| B. | Streamer theory |
| C. | Clump theory |
| D. | Only (a) and (b) |
| Answer» E. | |
| 2. |
While performing temperature rise tests, at any part of the bushing the steady temperature rise above the ambient air temperature should not exceed |
| A. | 20 °C |
| B. | 25 °C |
| C. | 35 °C |
| D. | 45 °C |
| Answer» E. | |
| 3. |
Within dielectric, an electron starting from the cathode will drift towards the anode and during this motion |
| A. | Gains energy from the field and loses during collision |
| B. | Gains energy during both motion and collision |
| C. | Loses energy during both motion and collision |
| D. | Loses energy from the field and gains during collision |
| Answer» B. Gains energy during both motion and collision | |
| 4. |
Which is having higher breakdown strength? |
| A. | Solid dielectrics |
| B. | Liquid dielectrics |
| C. | Gases dielectrics |
| D. | Equal in all |
| Answer» B. Liquid dielectrics | |
| 5. |
Which among the following is not an example of impregnants? |
| A. | Mineral oil |
| B. | Chlorinated diphenyl |
| C. | Vegetable oils |
| D. | None of these |
| Answer» E. | |
| 6. |
Treeing phenomenon is observed in |
| A. | Capacitors |
| B. | Cables |
| C. | Insulators |
| D. | Only (a) and (b) |
| Answer» E. | |
| 7. |
To protect the meter against high voltages in case the series resistance fails, the suitable protective device is |
| A. | Paper gap |
| B. | Neon glow tube |
| C. | Zener diode |
| D. | All of these |
| Answer» E. | |
| 8. |
The voltage which produces the loss of dielectric strength of insulation is known as |
| A. | Withstand voltage |
| B. | Disruptive discharge voltage |
| C. | Flashover voltage |
| D. | Impulse voltage |
| Answer» C. Flashover voltage | |
| 9. |
The voltage doubler circuit is suitable for the voltage up to |
| A. | 2V |
| B. | 4V |
| C. | 6V |
| D. | 8V |
| Answer» C. 6V | |
| 10. |
The Townsend mechanism explains the phenomenon of breakdown |
| A. | Only at low pressure |
| B. | Only at high pressure |
| C. | Only at very high pressure |
| D. | Only bat very low pressure |
| Answer» B. Only at high pressure | |
| 11. |
The thermal breakdown stresses are |
| A. | Lower under ac conditions than under dc condition |
| B. | Greater under ac condition than dc condition |
| C. | Equal in both condition |
| D. | None of these |
| Answer» B. Greater under ac condition than dc condition | |
| 12. |
The tests which is not performed under power frequency tests is |
| A. | Partial discharge tests |
| B. | Momentary withstand test |
| C. | Visible discharge tests |
| D. | Full wave withstand tests |
| Answer» E. | |
| 13. |
The temperature limit for class F insulation is |
| A. | 105°C |
| B. | 120°C |
| C. | 130°C |
| D. | 155°C |
| Answer» E. | |
| 14. |
The statistical time lag depends upon the |
| A. | Size of gap |
| B. | Quantity of radiation that produces the primary electrons |
| C. | Amount of pre-ionization preset gap |
| D. | All of these |
| Answer» E. | |
| 15. |
The spreading of spark channels during tracking, in the form of the branches of a tree is called |
| A. | Bunching |
| B. | Treeing |
| C. | sparking |
| D. | none of these |
| Answer» C. sparking | |
| 16. |
The sparkover voltage |
| A. | Increases with humidity |
| B. | decreases with the partial pressure of water vapour in air |
| C. | Humidity effect decreases with the size of spheres |
| D. | Humidity is minimum for uniform field gaps |
| Answer» B. decreases with the partial pressure of water vapour in air | |
| 17. |
The series capacitor peak voltmeter is suitable for |
| A. | Positive half cycle |
| B. | Negative half cycle |
| C. | Sinusoidal waveform |
| D. | All of these |
| Answer» E. | |
| 18. |
The ripple voltage for half wave rectifier is |
| A. | Smaller than that of full wave rectifier |
| B. | Larger than that of full wave rectifier |
| C. | Equal to that of full wave rectifier |
| D. | None of these |
| Answer» C. Equal to that of full wave rectifier | |
| 19. |
The resin bonded paper bushings are designed to operate at a maximum radial stress of |
| A. | 5 kV/cm |
| B. | 10 kV/cm |
| C. | 15 kV/cm |
| D. | 20 kV/cm |
| Answer» E. | |
| 20. |
The most commonly used insulating materials for low and medium voltage cables is |
| A. | Polyethylene |
| B. | Porcelain |
| C. | PVC |
| D. | Vulcanized rubber |
| Answer» D. Vulcanized rubber | |
| 21. |
The liquid dielectrics contain voids or cavities within the medium or at the boundaries between the dielectric and the electrodes. The electric field strength in the voids is |
| A. | Lower than that across the dielectric |
| B. | Higher than that across the dielectric |
| C. | Equal to that across the dielectric |
| D. | None of these |
| Answer» C. Equal to that across the dielectric | |
| 22. |
The increase in liquid hydrostatic pressure |
| A. | Increases the breakdown strength |
| B. | Decreases the breakdown strength |
| C. | Does not affect the breakdown strength |
| D. | None of these |
| Answer» B. Decreases the breakdown strength | |
| 23. |
The expected life at the rated stress can be determined by conducting long duration life tests at increased stress for |
| A. | Less than 1 hr |
| B. | 1 hr to about 1000 hr |
| C. | More than 1000 hr |
| D. | None of these |
| Answer» C. More than 1000 hr | |
| 24. |
The example of artificial fibre is |
| A. | Rayon |
| B. | Cotton |
| C. | Flax |
| D. | Silk |
| Answer» B. Cotton | |
| 25. |
The disadvantages of resonant transformers is |
| A. | Pure sine wave output |
| B. | No high power arcing |
| C. | No repeated flashovers |
| D. | Additional variable chokes |
| Answer» E. | |
| 26. |
The commonly used materials for HV insulation is |
| A. | Paper-oil insulation |
| B. | Polyester resin |
| C. | Ceramic |
| D. | PVC |
| Answer» B. Polyester resin | |
| 27. |
The attractive force between the electrodes of a parallel plate capacitor is |
| A. | Directly proportional to the square of the applied voltage between plates |
| B. | Directly proportional to the capacitance between the plates |
| C. | Inversely proportional to the square of the separation between the plates |
| D. | All of these |
| Answer» E. | |
| 28. |
The accuracy of the ac field strength depends on |
| A. | Harmonic content |
| B. | Atmospheric conditions |
| C. | Position of meter |
| D. | All of these |
| Answer» E. | |
| 29. |
Resins and varnishes are commonly used in |
| A. | Generators and motors |
| B. | Cables |
| C. | Transformers |
| D. | Circuit breakers |
| Answer» B. Cables | |
| 30. |
Liquids dielectrics are mainly used as |
| A. | Impregnants in high voltage cables |
| B. | In capacitors |
| C. | For filling up transformers |
| D. | All of these |
| Answer» E. | |
| 31. |
Insulation of dry type transformers is done using prepregs. It is manufactured by using |
| A. | Glass fibres |
| B. | Nomex |
| C. | Aramide papers |
| D. | All of these |
| Answer» E. | |
| 32. |
Insulation is necessary for the protection of equipment. Insulation is not necessary between |
| A. | Coils and earth |
| B. | Coils of different phases |
| C. | Turns in a coil |
| D. | None of these |
| Answer» E. | |
| 33. |
Inelastic collisions are those in which internal changes in energy take place within an atom or a molecule at the expenses of total kinetic energy of the colliding particle. Suitable example for inelastic collisions is/are |
| A. | Ionization |
| B. | Attachment |
| C. | Excitation |
| D. | All of these |
| Answer» E. | |
| 34. |
In Van de Graaff generators, the shape of high voltage electrode is nearly spherical to avoid |
| A. | High surface field gradients |
| B. | Corona |
| C. | Local discharges |
| D. | All of these |
| Answer» E. | |
| 35. |
In the half wave rectifier, charging current can be limited by using an additional |
| A. | Resistance in series with the secondary of the transformer |
| B. | Inductance in series with the primary of the transformer |
| C. | Inductance in series with the primary of the transformer |
| D. | Capacitance in series with the secondary of the transformer |
| Answer» B. Inductance in series with the primary of the transformer | |
| 36. |
In routine tests, the cable is tested by applying an ac voltage of |
| A. | 2 times the rated value |
| B. | 2.5 times the rated value |
| C. | 3 times the rated value |
| D. | 3.5 times the rated value |
| Answer» C. 3 times the rated value | |
| 37. |
In paper based laminated construction, the typical value of dielectric constant and dielectric loss factor is |
| A. | 3.5, 0.0015 |
| B. | 2.5, 0.0020 |
| C. | 3.5, 0.0025 |
| D. | 2.5, 0.0035 |
| Answer» D. 2.5, 0.0035 | |
| 38. |
In large impulse generators, the spark gaps are generally |
| A. | Sphere gaps |
| B. | Hemispherical gaps |
| C. | Square gaps |
| D. | Either (a) or (b) |
| Answer» E. | |
| 39. |
In equipments filled with liquid dielectric, heat is transferred mainly by |
| A. | Conduction |
| B. | Convection |
| C. | Radiation |
| D. | No heat transfers takes place |
| Answer» C. Radiation | |
| 40. |
In case of solid particles present in the liquid and in case of presence of only gas bubbles in liquids, the direction of force is towards |
| A. | Areas of maximum stress, areas of minimum stress |
| B. | Areas of maximum stress, areas of maximum stress |
| C. | Areas of minimum stress, areas of maximum stress |
| D. | Areas of minimum stress, areas of minimum stress |
| Answer» B. Areas of maximum stress, areas of maximum stress | |
| 41. |
In Breakdown tests, the tests voltages required for these tests are usually of the order of |
| A. | 0 – 10 kV |
| B. | 20 – 50 kV |
| C. | 50 – 100 kV |
| D. | 100 – 200 kV |
| Answer» D. 100 – 200 kV | |
| 42. |
In a series RLC circuit, the wave front and wave tail times are controlled by changing the value |
| A. | R only |
| B. | R and L simultaneously |
| C. | R and C simultaneously |
| D. | L and C simultaneously |
| Answer» C. R and C simultaneously | |
| 43. |
In a multistage impulse generator, for producing very high voltages, a bank of capacitors is |
| A. | Charged in parallel and then discharged in series |
| B. | Charged in series and then discharged in parallel |
| C. | Charged in parallel and then discharged in parallel only |
| D. | Charged in series and then discharged in series only |
| Answer» B. Charged in series and then discharged in parallel | |
| 44. |
Impulse testing of transformers is done using |
| A. | Full wave standard impulse |
| B. | Chopped wave standard impulse |
| C. | Half wave standard impulse |
| D. | Only (a) and (b) |
| E. | None of these |
| Answer» E. None of these | |
| 45. |
High temperature hydrocarbons have |
| A. | Higher boiling point and low viscosity |
| B. | Lower boiling point and high viscosity |
| C. | Lower boiling point and low viscosity |
| D. | Higher boiling point and high viscosity |
| Answer» E. | |
| 46. |
Formative time lag depends on the mechanism of the avalanche growth in gap. The formative time lag is usually |
| A. | Much shorter than the statistical time lag |
| B. | Much greater than the statistical time lag |
| C. | Equal to the statistical time lag |
| D. | None of these |
| Answer» B. Much greater than the statistical time lag | |
| 47. |
For very small cavities, discharge inception voltage |
| A. | Decreases as the cavity depth increases |
| B. | Increases as the cavity depth increases |
| C. | Remains unaffected as the cavity depth increases |
| D. | None of these |
| Answer» B. Increases as the cavity depth increases | |
| 48. |
For voltage measurements, the gap which gives the highest accuracy is |
| A. | Sphere gaps |
| B. | Field gaps |
| C. | Rod gaps |
| D. | None of these |
| Answer» B. Field gaps | |
| 49. |
For the measurement of ripple voltage in dc systems, the condition to be satisfied is |
| A. | ωCR >> 1 |
| B. | ωCR << 1 |
| C. | ωCR = 1 |
| D. | None of these |
| Answer» B. ωCR << 1 | |
| 50. |
For the measurement of radio interference voltages, the detector circuit is provided with a measuring device to measure |
| A. | Average value |
| B. | Peak value |
| C. | Quasi-peak value |
| D. | All of these. |
| Answer» E. | |