All Free Electrical Engineering MCQs with Answers
Every Electrical Engineering question in the bank, across all chapters, each with the correct answer and a written explanation. Free and unlimited, with no account needed.
3,143 questions · page 80 of 158
- A. presence of moisture
- B. working temperature
- C. time of application of the voltage
- D. all of the above
Explanation: Cable breakdown is affected by moisture, temperature and the duration of voltage application because these change insulation strength and…
Correct answer: all of the above- A. more perfect impregnation
- B. smaller overall size
- C. no ionisation, oxidation and formation of voids
- D. all of the above
Explanation: Oil fills voids in the insulation, improves impregnation and suppresses ionisation and oxidation, allowing a more compact cable design.
Correct answer: all of the above- A. annealed
- B. hardened and tempered
- C. hard drawn
- D. alloy with chromium
Explanation: Cable conductors are generally made from annealed copper because heat treatment makes copper soft, flexible and easy to draw into strands.
Correct answer: annealed- A. mica insulated
- B. paper insulated
- C. compressed oil or compressed gas insulated
- D. rubber insulated
- E. none of the above
Explanation: At 220 kV, conventional solid insulation becomes difficult to use economically because of high electric stress and capacitance.
Correct answer: compressed oil or compressed gas insulated- A. 2 cm
- B. 10 cm
- C. 50 cm
- D. 400 cm
Explanation: Keeping parallel power and communication cables about 50 cm apart reduces inductive and electromagnetic interference from the power cable.
Correct answer: 50 cm- A. low permittivity
- B. high resistivity
- C. high dielectric strength
- D. all of the above
Explanation: A good insulator has high resistivity to limit leakage, high dielectric strength to withstand voltage, and low permittivity to reduce…
Correct answer: all of the above- A. it is hygroscopic
- B. it has high capacitance
- C. it is an organic material
- D. none of the above
Explanation: Paper readily absorbs moisture because it is hygroscopic, and absorbed moisture sharply reduces its insulation resistance and dielectric…
Correct answer: it is hygroscopic- A. Yes
- B. No
Explanation: Capacitance grading uses layers of different dielectric materials, or sometimes graded insulation, to distribute electric stress more…
Correct answer: No- A. Yes
- B. No
Explanation: Natural rubber is latex obtained from the milky sap of tropical rubber trees, mainly Hevea brasiliensis.
Correct answer: Yes- A. Yes
- B. No
Explanation: Polyethylene has good dielectric strength, low dielectric loss and comparatively good resistance to ageing, so the statement that these…
Correct answer: No- A. Yes
- B. No
Explanation: Oil-filled cables require regular monitoring for oil pressure, leakage and replenishment, making their maintenance more difficult than…
Correct answer: Yes- A. becomes one-fourth
- B. becomes one-half
- C. becomes double
- D. remains unchanged
Explanation: Cable capacitance is proportional to its length because doubling the length doubles the area over which capacitive coupling occurs.
Correct answer: becomes double- A. prevent the moisture from entering the cable
- B. provide enough strength
- C. provide proper insulation
- D. none of the above
Explanation: The outer sheath primarily prevents moisture and other contaminants from entering the cable.
Correct answer: prevent the moisture from entering the cable1594. The breakdown of insulation of the cable can be avoided economically by the use of___________?
- A. inter-sheaths
- B. insulating materials with different dielectric constants
- C. both (A) and (B)
- D. none of the above
Explanation: Inter-sheaths and graded insulation using materials with different permittivities redistribute the electric field and reduce peak stress…
Correct answer: both (A) and (B)- A. minimize the stress
- B. avoid the requirement of good insulation
- C. provide proper stress distribution
- D. none of the above
Explanation: Inter-sheaths divide the insulation into sections and control the potential distribution, thereby making the electric stress more uniform.
Correct answer: provide proper stress distribution- A. lags the voltage by 90°
- B. leads the voltage by 90°
- C. lags the voltage by 180°
- D. leads the voltage by 180°
Explanation: A cable behaves capacitively, and current in a capacitor leads its voltage by 90 degrees. Therefore, the charging current leads the voltage.
Correct answer: leads the voltage by 90°- A. insulation may melt due to higher temperature
- B. skin effect dominates on the conductor
- C. of corona loss between conductor and sheath material
- D. there is a danger of breakdown of insulation due to the presence of voids
Explanation: Voids in solid insulation can ionise under high electric stress, producing partial discharges that gradually damage the insulation and…
Correct answer: there is a danger of breakdown of insulation due to the presence of voids- A. one half
- B. double
- C. four times
- D. none of the above
Explanation: Cable capacitance is directly proportional to the insulation permittivity, with geometry unchanged.
Correct answer: one half- A. 11 kV
- B. 33 kV
- C. 66 kV
- D. 132 kV
Explanation: Pressure cables use pressurised insulating material to suppress ionisation and void formation, but their construction becomes impractical…
Correct answer: 66 kV- A. between 2 and 3
- B. between 5 and 6
- C. between 8 and 10
- D. between 12 and 14
Explanation: Rubber has a relatively low relative permittivity, typically about 2 to 3, unlike materials such as mica or porcelain whose values are…
Correct answer: between 2 and 3