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 35 of 158
- A. low power factor
- B. high power factor
- C. high over load capacity
- D. any of the above
Explanation: A small air gap reduces the reluctance of the magnetic circuit and therefore lowers the magnetizing current.
Correct answer: high power factor682. The efficiency of a machine should be as ____________ as possible to reduce the operating cost?
- A. high
- B. low
- C. either of the above
- D. none of the above
Explanation: Higher efficiency means less input power is wasted as heat and losses for the same useful output.
Correct answer: high- A. small size machines
- B. medium size machines
- C. large size machines
- D. any of the above
Explanation: Machines rated from a few kilowatts to approximately 250 kW are generally classified as medium-size machines.
Correct answer: medium size machines- A. small
- B. medium
- C. large
- D. any of the above.
Explanation: In large machines, the shaft is relatively long and flexible, so its deflection and critical speed become important design considerations.
Correct answer: large- A. Diamond
- B. High speed steel
- C. Mild steel
- D. Cast iron
Explanation: Cast iron has strong internal friction and a relatively non-elastic structure, allowing it to absorb vibrational energy effectively.
Correct answer: Cast iron686. Copper, even though costly, finds use in the windings of electrical machines because_____________?
- A. copper points offer low contact resistance
- B. copper can be easily soldered and welded
- C. copper windings are less bulky and the machines become compact
- D. all of the above
Explanation: Copper combines very high conductivity with good solderability and weldability, while its low resistivity permits smaller, less bulky…
Correct answer: all of the above- A. Where lubrication is difficult or im-possible
- B. Where corrosive chemical action exists
- C. Where high temperature exists
- D. All of the above
Explanation: Carbon bearings are suitable where oil or grease lubrication is impractical, and they withstand corrosive chemicals and relatively high…
Correct answer: All of the above- A. Speed of the machine
- B. Contact pressure
- C. Surface conditions of brush and commutator
- D. Excessive sparking
- E. All of the above
Explanation: Brush wear depends on speed, contact pressure, brush and commutator surface condition, and sparking.
Correct answer: All of the above- A. copper
- B. kanthal
- C. manganin
- D. nichrome
Explanation: Starter coils require relatively high resistance to limit current, so manganin wire is used because it has high resistivity and a low…
Correct answer: manganin- A. To avoid initial rush of current
- B. To avoid change in kW rating with temperature
- C. Both (A) and (B)
- D. Either (A) or (B)
Explanation: A low temperature coefficient keeps the element resistance nearly constant as it heats, reducing the cold-start current surge and…
Correct answer: Both (A) and (B)- A. zero
- B. 0.707 lagging
- C. unity
- D. 0.707 leading
Explanation: Arc furnaces behave largely as inductive loads and commonly operate at a lagging power factor near 0.7.
Correct answer: 0.707 lagging- A. it is filled below core level
- B. it is filled above core level
- C. it is fully empty
- D. none of the above
Explanation: The Ajax-Wyatt furnace is a core-type induction furnace, so the molten or conducting charge must surround the core sufficiently to form…
Correct answer: it is filled above core level- A. Variation of resistance
- B. Variation of voltage
- C. Periodical switching on and off of the supply
- D. All of the above methods
Explanation: Furnace temperature can be regulated by changing resistance, varying the applied voltage, or switching the supply periodically.
Correct answer: All of the above methods- A. to stabilize the arc
- B. to imprpve, power factor
- C. to reduce severity of the surge
- D. none of the above
Explanation: The choke adds inductive reactance and limits rapid current changes, helping maintain a more stable arc.
Correct answer: to stabilize the arc- A. induction heating of steel
- B. dielectric heating
- C. induction heating of brass
- D. resistance heating
Explanation: Induction heating of steel produces heat through both eddy-current loss and hysteresis loss because steel is electrically conducting and…
Correct answer: induction heating of steel- A. bad, good
- B. bad, bad
- C. good, bad
- D. good, good
Explanation: Mica transfers heat from the heating element to the press surface while electrically insulating the user and metal parts.
Correct answer: good, bad697. In heating the ferromagnetic material by induction heating, heat is produced due to_____________?
- A. induced current flow through the charge
- B. hysteresis loss taking place below curie temperature
- C. due to hysteresis loss as well as eddy current loss takingplace in the charge
- D. none of the above factors
Explanation: In ferromagnetic materials below the Curie temperature, the alternating magnetic field causes both induced eddy currents and repeated…
Correct answer: due to hysteresis loss as well as eddy current loss takingplace in the charge- A. Unity
- B. Low, lagging
- C. Low, leading
- D. Any of the above
Explanation: The furnace transformer and arc circuit have considerable inductive reactance, so the current lags the voltage and the power factor is low…
Correct answer: Low, lagging- A. The amount of heat generated can be controlled accurately
- B. Heat at very high rate can be gene-rated
- C. The area of the surface over which heat is produced can be accurately controlled
- D. All of the above
Explanation: Eddy-current heating permits rapid heating, precise control of generated heat, and concentration of heat over a selected surface region.
Correct answer: All of the above- A. Annealing of metals
- B. Melting of ferrous metals
- C. Heating of liquids in electric kettle
- D. Drying of paints and varnishes
Explanation: Radiant heating transfers heat mainly through infrared radiation, making it especially suitable for surface processes such as drying…
Correct answer: Drying of paints and varnishes