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 42 of 158
821. Excessive formation of lead sulphate on the surface of the plates happens because of___________?
- A. allowing a battery to stand in discharged condition for a long time
- B. topping up with electrolyte
- C. persistent undercharging
- D. low level of electrolyte
- E. all above
Explanation: Leaving a battery discharged, persistent undercharging, an inadequate electrolyte level, or using electrolyte improperly for topping up…
Correct answer: all above- A. active
- B. passive
- C. inert
- D. dielectric
Explanation: The substances that undergo chemical changes during charging and discharging to store and release electrical energy are called active…
Correct answer: active- A. reduces specific gravity of the electrolyte
- B. increases specific gravity of the electrolyte
- C. produces excessive gassing
- D. increases the temperatureHire Civil Engineers
Explanation: Undercharging leaves some lead sulphate unconverted and keeps the charging reaction incomplete, so the electrolyte remains less…
Correct answer: reduces specific gravity of the electrolyte- A. two rate charge control
- B. trickle charge
- C. floating charge
- D. an equalizing charge
Explanation: A two-rate charge-control system switches or regulates the charging current between upper and lower limits, preventing excessive current…
Correct answer: two rate charge control- A. amperes
- B. ampere-hours
- C. watts
- D. watt-hours
Explanation: Battery capacity is the amount of charge it can deliver, calculated as current multiplied by time, so its unit is ampere-hour (Ah).
Correct answer: ampere-hours- A. produces excessive gassing
- B. loosens the active material
- C. increases the temperature resulting in buckling of plates
- D. all above
Explanation: Overcharging causes excessive gassing, heats the cell and may buckle the plates; it can also loosen the active material.
Correct answer: all above- A. its chemical constituents
- B. on the strength of its electrolyte
- C. its temperature
- D. all above
Explanation: Cell open-circuit voltage is governed by the electrode and electrolyte chemistry, while electrolyte strength and temperature also affect…
Correct answer: all above- A. NaOH
- B. onlyH2S04
- C. only water
- D. dilute H2SO4
Explanation: A lead-acid cell uses sulfuric acid diluted with water as its electrolyte.
Correct answer: dilute H2SO4- A. charged state
- B. discharged state
- C. both (A) and (B)
- D. active state
Explanation: During discharge, sulfuric acid is consumed and water is formed, so the electrolyte specific gravity falls.
Correct answer: discharged state- A. copper
- B. lead
- C. iron
- D. silver oxide
Explanation: The Edison, or nickel-iron, cell uses iron as the negative-plate material and nickel oxide as the positive material.
Correct answer: iron- A. less than
- B. more than
- C. equal to
- D. none of the above
Explanation: Lead-acid cells have lower internal resistance than Edison cells, allowing them to supply comparatively larger current.
Correct answer: less than- A. NaOH
- B. KOH
- C. HC1
- D. HN03
Explanation: The Edison cell uses potassium hydroxide, KOH, as its alkaline electrolyte.
Correct answer: KOH- A. 40%
- B. 60%
- C. 70%
- D. 80%
Explanation: An Edison nickel-iron cell has a relatively low ampere-hour efficiency because charging losses and gas evolution are significant; its…
Correct answer: 80%- A. 1.4 V
- B. 1 V
- C. 0.9 V
- D. 0.8 V
Explanation: A fully charged Edison cell has a nominal e.m.f. of about 1.4 V, higher than the approximately 1.2 V value associated with its normal…
Correct answer: 1.4 V- A. two
- B. three
- C. four
- D. five
Explanation: Alkaline cells generally have higher internal resistance than lead-acid cells, commonly taken as approximately five times as high in…
Correct answer: five- A. rate of discharge
- B. temperature
- C. density of electrolyte
- D. quantity of active materials
- E. all above
Explanation: Cell capacity changes with discharge rate, temperature, electrolyte density, and the amount of active material, so all the listed factors…
Correct answer: all above- A. 20 to 30%
- B. 40 to 50%
- C. 60 to 70%
- D. 90 to 95%
Explanation: Lead-acid batteries have a high ampere-hour efficiency, normally around 90 to 95%; their watt-hour efficiency is lower because of voltage…
Correct answer: 90 to 95%- A. dull
- B. reddish
- C. bright
- D. milky
Explanation: Near full charge, vigorous gassing produces many fine gas bubbles in the electrolyte, giving it a milky appearance.
Correct answer: milky- A. silver oxide
- B. lead oxide
- C. lead
- D. zinc powder
Explanation: In a silver-zinc cell, silver oxide forms the positive-plate active material, while zinc serves as the negative-plate material.
Correct answer: silver oxide- A. 1 V
- B. 1.2 V
- C. 1.7 V
- D. 2.1 V
Explanation: An alkaline cell has a nominal voltage near 1.2 V, but its average charging voltage is about 1.7 V because charging must overcome its…
Correct answer: 1.7 V