Free Electronics and Devices MCQs with Answers

• A. small
• B. very small
• C. large
• D. zero

Explanation: A lossy capacitor has appreciable power loss, represented by a series equivalent resistance that is relatively large compared with that of…

• A. Mica capacitor
• B. Electrolytic capacitor
• C. Ceramic capacitor
• D. Paper capacitor

Explanation: Electrolytic capacitors have a shorter shelf life because their electrolyte can dry out or chemically deteriorate even when they are not…

• A. Distance between plates
• B. Area of the plates
• C. Nature of dielectric
• D. Thickness of the plates

Explanation: For a parallel-plate capacitor, C = εA/d, so capacitance depends on plate area, separation, and dielectric permittivity.

• A. Paper capacitor
• B. Ceramic capacitor
• C. Silver plated mica capacitor
• D. None of the above

Explanation: Silver-plated mica capacitors have excellent stability because mica has very low dielectric loss and a small temperature coefficient.

• A. resistor
• B. insulator
• C. good conductor
• D. semi conductor

Explanation: A dielectric is a material that does not provide significant conduction current, but it becomes polarized in an electric field.

• A. distance between plates
• B. area of plates
• C. thickness of plates
• D. all of the above

Explanation: The ideal relation C = εA/d includes plate area, separation, and dielectric permittivity, but not the physical thickness of the plates.

• A. increase the efficiency
• B. increase the current capacity
• C. increase the voltage output
• D. increase the internal resistance

Explanation: Parallel connection keeps the cell voltage approximately unchanged while adding the available current capacities.

• A. Brake light
• B. Self starter
• C. Parking lights
• D. Spark plugs

Explanation: The self-starter motor draws a very large current for a short time, so it is the automobile battery's major load.

• A. 10% of capacity
• B. 20% of capacity
• C. 30% of capacity
• D. 40% of capacity

Explanation: A commonly specified normal charging rate for a storage battery is about one-tenth of its ampere-hour capacity, known as a 10-hour rate.

• A. water is poured into acid
• B. acid is poured into water
• C. anyone of the two can be added to other chemical

Explanation: Acid must be added slowly to water, never water to concentrated acid, because the mixing heat can cause sudden boiling and dangerous…

• A. chlorine
• B. dust particles
• C. lead crystals
• D. iron

Explanation: Iron is a harmful and common impurity in lead-acid battery electrolyte, where it can increase self-discharge and interfere with normal…

• A. prevent local heating
• B. prevent short-circuiting
• C. reduce path resistance
• D. prevent corrosion

Explanation: Petroleum jelly seals battery terminals from moisture and corrosive vapours, reducing oxidation and corrosion.

• A. Lead-acid
• B. Mercury oxide
• C. Carbon-zinc
• D. Silver-oxide

Explanation: A lead-acid cell has reversible charge and discharge reactions, so it can be recharged repeatedly.

• A. they have same e.m.f.
• B. they have same make
• C. they have same ampere-hour capacity
• D. they have identical internal resistance

Explanation: Parallel batteries must have the same e.m.f. so that one battery does not force an excessive circulating current through the other.

• A. Dilute H2S04
• B. Concentrated H2SO4
• C. Water
• D. Any of the above

Explanation: Water has a specific gravity of about 1, while even dilute sulphuric acid is denser than water.

• A. to reduce evaporation of water from electrolyte
• B. to exclude dirt and foreign matter from the electrolyte
• C. to discharge both of the above functions
• D. to discharge none of the above functions

Explanation: The battery cover seals the electrolyte from both water loss by evaporation and entry of dirt or other foreign matter.

• A. Manganese-alkaline
• B. Carbon-zinc
• C. Lithium
• D. Mercury

Explanation: Lithium primary cells typically provide about 3 V per cell, whereas carbon-zinc, alkaline, and mercury cells are generally around 1.5 V.

• A. Two electrodes of different meta's should be inserted in the electrolyte, not touching each other
• B. Electrolyte must chemically react with one of the electrodes
• C. Electrolyte liquid or paste should be conducting
• D. All above three conditions are necessary

Explanation: A conventional cell needs separated electrodes, an ionically conducting electrolyte, and a chemical reaction that produces charge…

• A. boiling of electrolyte due to gassing
• B. warping of plates
• C. damage to separators, cell caps covers and battery case due to excessive temperature
• D. all above

Explanation: A sulphated battery has poor charge acceptance, so high-rate charging causes excessive gassing and heating.

• A. increases
• B. decreases
• C. remains the same
• D. becomes zero

Explanation: During charging, lead sulfate is converted back into lead, lead dioxide and sulfuric acid.