Cells and Batteries MCQ Quiz - Objective Question with Answer for Cells and Batteries - Download Free PDF

Explanation:

Nickel-Iron Cell Discharging Process

Definition: A Nickel-Iron (Ni-Fe) cell, also known as an Edison cell, is a type of rechargeable battery that utilizes nickel oxide hydroxide as the positive electrode and iron as the negative electrode. During the discharging process, chemical reactions occur at both electrodes to produce electrical energy.

Working Principle During Discharging: In a Nickel-Iron cell, the discharging process involves the following electrochemical reactions:

At the positive electrode (cathode), nickel oxide hydroxide (NiOOH) is reduced to nickel hydroxide (Ni(OH)₂):
NiOOH + H₂O + e^- → Ni(OH)₂ + OH^-

At the negative electrode (anode), iron (Fe) is oxidized to iron hydroxide (Fe(OH)₂):
Fe + 2OH^- → Fe(OH)₂ + 2e^-

These reactions result in the flow of electrons through an external circuit, generating electrical energy that can be utilized by connected devices. The overall cell reaction during discharge can be summarized as:
NiOOH + Fe + H₂O → Ni(OH)₂ + Fe(OH)₂

Applications: Nickel-Iron cells are commonly used in off-grid and renewable energy storage systems, emergency lighting, railway signaling, and other applications where long life and robustness are critical.

Correct Option Analysis:

The correct option is:

Option 2: Iron at the negative electrode is oxidized to iron oxide, and nickel at the positive electrode is reduced to nickel hydroxide.

This option correctly describes the electrochemical reactions occurring during the discharging process of a Nickel-Iron cell. Iron at the negative electrode undergoes oxidation, while nickel oxide hydroxide at the positive electrode undergoes reduction, leading to the generation of electrical energy.

Additional Information

To further understand the analysis, let’s evaluate the other options:

Option 1: Nickel at the positive electrode is reduced to metallic nickel, and iron hydroxide at the negative electrode is oxidized.

This option is incorrect because, during the discharging process, nickel oxide hydroxide is reduced to nickel hydroxide, not metallic nickel. Additionally, iron is oxidized to iron hydroxide, not iron hydroxide being oxidized.

Option 3: Nickel hydroxide at the positive electrode is reduced to metallic nickel, and iron is oxidized at the negative electrode.

This option is incorrect because nickel hydroxide is not reduced to metallic nickel during discharging. Instead, nickel oxide hydroxide is reduced to nickel hydroxide.

Option 4: Iron at the negative electrode is reduced to metallic iron, and nickel hydroxide at the positive electrode is oxidized.

This option is incorrect because, during discharging, iron is oxidized to iron hydroxide, not reduced to metallic iron. Additionally, nickel hydroxide is not oxidized during discharging; instead, nickel oxide hydroxide is reduced to nickel hydroxide.

The correct option is 1

Concept:

Primary cell:

• A primary cell or battery is one that cannot easily be recharged after one use and is discarded following discharge.
• Most primary cells utilize electrolytes that are contained within absorbent material or a separator (i.e. no free or liquid electrolyte) and are thus termed dry cells.
• Two examples of primary cells are Daniel's cell, and. Leclanche cell.
• The cell is not used to store electrical energy in the form of chemical energy.

Explanation:

• A primary cell is a cell that is designed to be used once and discarded, not recharged with electricity, and reused like a secondary cell.
• In general, the electrochemical reaction occurring in the cell is not reversible, so these cells cannot be recharged.​

Additional InformationSecondary cell:

• A secondary cell is a type of cell that can be electrically recharged by passing current in the opposite direction of the circuit.
• One of the best examples of secondary cells is an alkaline battery.
• Energy in an alkaline battery is obtained from the interaction of zinc metal and manganese dioxide.
• These batteries live longer and have a greater energy density. 
• It converts electrical energy into chemical energy when current is passed in it (i.e. during charging), while it converts chemical energy into electrical energy when current is drawn from it (i.e., during discharging).

The correct answer is: 4) The amount of charge a battery can store and deliver over a specific time period
Explanation:

The capacity of a battery is defined as:

• The total electric charge (in ampere-hours, Ah) it can store and deliver under specified conditions (e.g., discharge rate, temperature).

• Example: A 10 Ah battery can theoretically deliver 1A for 10 hours or 2A for 5 hours.

Explanation:

Sediment Accumulation in Lead Acid Batteries

Definition: In lead-acid batteries, sediment accumulation refers to the buildup of solid material at the bottom of the battery cells over time. This sediment primarily consists of disintegrated active material from the battery plates, which can affect the battery's performance and lifespan if not managed properly.

Composition of Sediment: The sediment in lead-acid batteries is largely made up of lead compounds that have fallen off from the plates during the charge and discharge cycles. However, it is important to identify the specific types of lead compounds that make up this sediment to understand its impact and manage it effectively.

Correct Option Analysis:

The correct option is:

Option 3: Antimony lead alloy

This option is correct because the sediment that accumulates at the bottom of lead-acid batteries often contains antimony lead alloy. Antimony is commonly added to the lead in battery plates to enhance their mechanical strength and resistance to corrosion. Over time, small particles of this alloy can break off and settle at the bottom of the battery. This sediment can affect the battery's performance by potentially causing short circuits between the plates if it builds up excessively.

Additional Information

To further understand the analysis, let’s evaluate the other options:

Option 1: Lead peroxide

Lead peroxide (PbO₂) is an active material used in the positive plates of lead-acid batteries. While it can contribute to the sediment, it is not the primary component. Lead peroxide can degrade into other compounds, which may then become part of the sediment, but it is not the main constituent of the sediment that accumulates at the bottom of the battery.

Option 2: Lead sulphate

Lead sulphate (PbSO₄) forms on both the positive and negative plates during the discharge cycle of a lead-acid battery. While lead sulphate can contribute to the sediment, especially if the battery is not properly maintained and undergoes excessive cycling, it is not the primary component. Lead sulphate can dissolve back into the electrolyte during the recharge cycle, reducing its presence in the sediment.

Option 4: Graphite

Graphite is not typically found in lead-acid batteries. It is not used in the construction of the plates or other components of the battery. Therefore, graphite is not a constituent of the sediment that accumulates at the bottom of lead-acid batteries.

Conclusion:

Understanding the composition of the sediment in lead-acid batteries is crucial for maintaining their performance and longevity. The correct answer, antimony lead alloy, highlights the importance of additives in the battery plates and their potential impact on sediment formation. Proper maintenance and periodic inspection of the sediment can help prevent performance issues and extend the life of the battery.

Explanation:

Active Material of a Lead Acid Cell

Definition: In a lead acid cell, the active materials are the substances that undergo electrochemical reactions to store and release electrical energy. These materials are crucial for the cell's operation, as they participate directly in the charge and discharge processes.

Correct Option Analysis:

The correct option is:

Option 1: Sponge lead

This option accurately identifies one of the primary active materials in a lead acid cell. Sponge lead, also known as porous lead, is used as the negative active material in the cell. During the discharge process, the sponge lead reacts with sulfuric acid to form lead sulfate, releasing electrical energy. During the charging process, the lead sulfate is converted back into sponge lead, allowing the cell to store energy once again.

Additional Information

To further understand the analysis, let’s evaluate the other options:

Option 2: Semiconductor

Semiconductors are materials with electrical conductivity between that of conductors and insulators. They are used in electronic components such as diodes, transistors, and integrated circuits. However, they are not used as active materials in lead acid cells. The electrochemical reactions in a lead acid cell do not involve semiconductors.

Option 3: Resistance

Resistance is a property of materials that opposes the flow of electric current. It is not a material itself but a characteristic that can be found in various materials, such as resistors in electronic circuits. In the context of a lead acid cell, resistance is not an active material but a factor that can affect the cell's performance by causing energy losses. The active materials in a lead acid cell are those that participate in the electrochemical reactions, not materials exhibiting resistance.

Option 4: Wrought iron

Wrought iron is an iron alloy with a very low carbon content, known for its toughness, malleability, and corrosion resistance. It is used in various structural and decorative applications. However, wrought iron is not used as an active material in lead acid cells. The materials involved in the electrochemical reactions of a lead acid cell are lead, lead dioxide, and sulfuric acid, not wrought iron.

Conclusion:

Understanding the composition and function of a lead acid cell's active materials is crucial for appreciating its operation. The correct option, sponge lead, plays a vital role as the negative active material in the cell's electrochemical reactions, enabling the storage and release of electrical energy. The other options, including semiconductors, resistance, and wrought iron, do not pertain to the active materials in a lead acid cell and are unrelated to its electrochemical processes.

By correctly identifying the active materials in lead acid cells, one can better understand their functioning, applications, and limitations in various energy storage and power supply scenarios.

Whenever a storage battery is used as an emergency reserve, as in the case of un-interrupted power supply (UPS), it is necessary to keep the batteries fully charged and ready for use at any time if the mains supply fails.

A fully charged battery, which is not connected to any load is expected to maintain its terminal voltage. But, due to internal leakage in the battery and other open circuit losses, the battery voltage slowly falls even in idle or open circuit condition.

Therefore, to keep it in fully charged condition, the battery should be supplied with a charging current which is small and just sufficient to compensate the idle condition or open circuit losses. This small current charging is known as Trickle charging.

Trickle charging keeps the battery always fully charged and in ready to use condition, so that, the battery can be fully made use of in emergency conditions.​

Nickel-Iron cell:

• Nickel-iron cell is in the charged condition, the active material on positive plates is Ni(OH)₄ and that on the negative plates is iron (Fe)
• The positive and negative plates are held in a nickel-plated steel container; the plates being insulated from each other by hard rubber strips
• The container contains 21 per cent solution of KOH (electrolyte) to which is added a small amount of lithium hydrate (LiOH) for increasing the capacity of the cell
• It has lesser weight and longer life than that of a lead-acid cell
• The emf of this cell is about 1.36 V
• These cells are very suitable for portable work

The correct answer is M. Faraday.

• Michael Faraday has given laws of electrolysis.
• Faraday’s laws of electrolysis, are two quantitative laws used to express magnitudes of electrolytic effects, first described by the English scientist Michael Faraday in 1833.
• The laws state that:
  • The amount of chemical change produced by the current at an electrode-electrolyte boundary is proportional to the quantity of electricity used.
  • The amounts of chemical changes produced by the same quantity of electricity in different substances are proportional to their equivalent weights.

Key Points

• The electrochemical cell which facilitates a chemical reaction through the induction of electrical energy is known as an electrolytic cell.

 Cells:

• Voltaic cell
• Carbon-zinc cell (Leclanche cell and Dry cell)
• Alkaline cell
• Mercury cell
• Silver oxide cell
• Lithium cell

Two of the advantages of lithium cells over other primary cells are:

• Longer shelf life - up to 10 years
• Higher energy-to-weight ratios up to 350 WH/Kg

There are two ways of expressing the efficiency of a secondary cell.

Ampere hour efficiency: It is the ratio of output ampere-hours to input ampere-hours of the cell.

Ampere hour efficiency, \({\eta _{Ah}} = \frac{{ampere\;hours\;provided\;on\;discharge}}{{ampere - hours\;of\;charge}} \times 100\)

The ampere-hour efficiency of a lead-acid cell is about 90%.

Watt-hour efficiency: It is the ratio of output energy to the input energy of the cell.

Watt-hour efficiency, \({\eta _{wh}} = \frac{{energy\;given\;on\;discharge}}{{energy\;input\;of\;charge}} \times 100\)

The watt-hour efficiency of a lead-acid cell varies between 70% to 80%.

Important point:

The efficiency of a lead-acid cell depends upon the following factors:

• Rate of charge and discharge
• Internal resistance and polarisation
• The time interval between the end of discharge and the commencement of recharge.
• Temperature

Ni-Cd battery:

The active materials in a Nickle-Cadmium Battery are:

• Nickel Hydroxide Ni (OH)₂ acts as the positive plate, its preparation, and composition are the same as the positive plate in the Nickle-Iron battery
• The spongy Cadmium (Cd) acts as a negative plate
• Although the electrolyte does not enter into a chemical reaction with plates or any other chemical, it is made up of Potassium Hydroxide (KOH) solution with a specific gravity of 1.2
   

Reaction during Discharge or Under Charged state:

Positive Plate: Ni (OH)₄ + 2K → Ni (OH)₂ + 2 KOH

Negative Plate: Cd + 2 OH → Cd (OH)₂

Reaction during Charging or under Discharge state:

Positive Plate: Ni (OH)₂ + 2 OH → Ni (OH)₄

Negative Plate: Cd (OH)₂ + 2 K → Cd + 2 KOH

Advantages:

• Good performance in high-discharge and low-temperature applications
• Long shelf and use life

Disadvantages:

• Cost is more than the lead-acid battery
• These batteries have lower power densities

There are basically four major rechargeable batteries

• Lithium-ion (Li-ion)
• Nickel Cadmium (Ni-Cd)
• Nickel-Metal Hydride (Ni-Cd)
• Lead-Acid

Lithium-ion battery:

• Lithium-ion batteries are a type of rechargeable battery in which lithium ions from the negative electrode migrate to the positive electrode during discharge and migrate back to the negative electrode when the battery is being charged
• They are used in different portable appliances including mobile phones, smart devices and several other battery appliances used at home
• They also find applications in aerospace and military applications due to their lightweight nature

Nickel-cadmium battery:

• The nickel-cadmium battery (Ni-Cd battery or NiCad battery) is a type of rechargeable battery which is developed using nickel oxide hydroxide and metallic cadmium as electrodes
• The small packs are used in portable devices, electronics and toys while the bigger ones find application in aircraft starting batteries, electric vehicles and standby power supply

Nickel-metal hydride battery:

• Nickel metal hydride (Ni-MH) is a type of chemical configuration used for rechargeable batteries
• The chemical reaction at the positive electrode of batteries is similar to that of the nickel-cadmium cell (Ni-Cd), with both battery types using the same nickel oxide hydroxide (NiOOH)
• NiMH batteries find application in high drain devices because of their high capacity and energy density

Lead-acid battery:

• Lead-acid type is the most widely used type of car batteries
• Primarily, these are regarded as the high-performance car batteries because of their affordability and ability to provide a large volume of current that is needed to start the car
• These are a low-cost reliable power workhorse used in heavy-duty applications
• They are usually very large and because of their weight, they’re always used in non-portable applications such as solar-panel energy storage, vehicle ignition and lights, backup power and load levelling in power generation/distribution.

Additional Information

Primary cells: It is a cell that once it has been discharged, cannot be recharged. Primary cells are called as dry cells because they have solid or molten electrolyte.

These are light in weight and have less cost.

Secondary cells: It is the one that can be electrically recharged after use to their original pre-discharge condition. Normally secondary cells are wet cells.

These are heavy in weight and have a high initial cost.

An alkaline cell is not a rechargeable cell.