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Questions and Answers
What is the primary role of the negative terminal in both electrolytic and galvanic cells?
What is the primary role of the negative terminal in both electrolytic and galvanic cells?
Which of the following statements about alkaline cells is NOT true?
Which of the following statements about alkaline cells is NOT true?
What distinguishes secondary cells from primary cells?
What distinguishes secondary cells from primary cells?
In the construction of lead-acid batteries, what is the purpose of the separators?
In the construction of lead-acid batteries, what is the purpose of the separators?
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Which of the following is a characteristic of alkaline cells?
Which of the following is a characteristic of alkaline cells?
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What unique feature do lead-acid batteries have in terms of plate configuration?
What unique feature do lead-acid batteries have in terms of plate configuration?
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Which of the following types of secondary cells is NOT commonly recognized?
Which of the following types of secondary cells is NOT commonly recognized?
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What is the typical outcome of charging a secondary cell?
What is the typical outcome of charging a secondary cell?
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What occurs when a lead-acid battery is discharged significantly over time?
What occurs when a lead-acid battery is discharged significantly over time?
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During the charging process of a lead-acid battery, what happens to the sulphate on the plates?
During the charging process of a lead-acid battery, what happens to the sulphate on the plates?
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What is the approximate specific gravity of the electrolyte when the battery is fully charged?
What is the approximate specific gravity of the electrolyte when the battery is fully charged?
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What is a critical effect of discharging a lead-acid battery below 10.5 volts?
What is a critical effect of discharging a lead-acid battery below 10.5 volts?
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What is the role of vent plugs during the final charging phase?
What is the role of vent plugs during the final charging phase?
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What happens to the internal resistance of a lead-acid battery?
What happens to the internal resistance of a lead-acid battery?
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What is necessary to prevent damage when charging a lead-acid battery?
What is necessary to prevent damage when charging a lead-acid battery?
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Which statement accurately reflects the chemical changes during charging in a lead-acid battery?
Which statement accurately reflects the chemical changes during charging in a lead-acid battery?
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How should a lead-acid battery be maintained while in service?
How should a lead-acid battery be maintained while in service?
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What is the primary consequence of increased internal resistance in a lead-acid battery?
What is the primary consequence of increased internal resistance in a lead-acid battery?
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What is the key advantage of using series-parallel connected cells over single cells?
What is the key advantage of using series-parallel connected cells over single cells?
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What occurs during normal charging when a battery experiences gassing?
What occurs during normal charging when a battery experiences gassing?
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Which statement correctly describes the function of a hydrometer in the context of battery maintenance?
Which statement correctly describes the function of a hydrometer in the context of battery maintenance?
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What is the Seebeck effect in relation to thermocouples?
What is the Seebeck effect in relation to thermocouples?
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How is the potential difference measured in a thermocouple?
How is the potential difference measured in a thermocouple?
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What is the main purpose of the electrolyte in a cell?
What is the main purpose of the electrolyte in a cell?
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Which statement accurately describes a secondary cell?
Which statement accurately describes a secondary cell?
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In series connections of batteries, which of the following is true?
In series connections of batteries, which of the following is true?
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What is the primary consequence of using batteries in parallel?
What is the primary consequence of using batteries in parallel?
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What component typically serves as the negative terminal in a dry cell?
What component typically serves as the negative terminal in a dry cell?
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Which of the following substances is used to neutralize alkaline spills?
Which of the following substances is used to neutralize alkaline spills?
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What is a defining characteristic of dry cells compared to wet cells?
What is a defining characteristic of dry cells compared to wet cells?
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What is NOT a function of the electrodes in a cell?
What is NOT a function of the electrodes in a cell?
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What is the significance of connecting cells in series-parallel configurations?
What is the significance of connecting cells in series-parallel configurations?
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Which of the following statements about primary cells is correct?
Which of the following statements about primary cells is correct?
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What is the primary characteristic of the internal resistance of a Nickel-Cadmium cell compared to a Lead-acid cell?
What is the primary characteristic of the internal resistance of a Nickel-Cadmium cell compared to a Lead-acid cell?
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Which electrolyte composition is used in Nickel-Cadmium cells?
Which electrolyte composition is used in Nickel-Cadmium cells?
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What happens to the negative terminal of a Nickel-Cadmium cell when it is discharged?
What happens to the negative terminal of a Nickel-Cadmium cell when it is discharged?
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What is a notable benefit of using a Nickel-Cadmium cell at high discharge rates?
What is a notable benefit of using a Nickel-Cadmium cell at high discharge rates?
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Which statement accurately describes the state of the Nickel-Cadmium cell's electrolyte during the charging process?
Which statement accurately describes the state of the Nickel-Cadmium cell's electrolyte during the charging process?
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How does the charge retention capability of a Nickel-Cadmium cell compare to that of a Lead-acid cell?
How does the charge retention capability of a Nickel-Cadmium cell compare to that of a Lead-acid cell?
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What potential danger arises from high charging cycles in Nickel-Cadmium cells?
What potential danger arises from high charging cycles in Nickel-Cadmium cells?
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Which of the following statements is true regarding the maintenance of Nickel-Cadmium cells?
Which of the following statements is true regarding the maintenance of Nickel-Cadmium cells?
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What is the nominal open-circuit cell voltage for a Nickel-Cadmium cell?
What is the nominal open-circuit cell voltage for a Nickel-Cadmium cell?
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What defines the effect of the age of the electrolyte in Nickel-Cadmium cells?
What defines the effect of the age of the electrolyte in Nickel-Cadmium cells?
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Study Notes
Electrolytic and Galvanic Cells
- Oxidation occurs at the positive terminal, which has a positive charge.
- Reduction occurs at the negative terminal, which has a negative charge.
Alkaline Cells
- Similar to Carbon-Zinc cells, but use an alkali solution (Potassium Hydroxide) as the electrolyte.
- Deliver sustained high currents.
- More efficient than Carbon-Zinc cells.
- Have a longer shelf life.
- Perform better in cold weather and under drain.
- Do not produce any gaseous products.
- May be rechargeable.
- Types: Mercury Oxide, Silver Oxide, Zinc-air.
Secondary Cells
- Electrodes and electrolyte are altered when the cell delivers current.
- Can be restored to their original state by charging.
- Charging involves an electric current passed through the cell in the opposite direction of discharge.
- Sometimes known as wet cells.
- Common example is an automobile battery.
Some Basic Types of Secondary Cells
- Lead-acid
- Nickel-cadmium
- Silver-Zinc
- Silver-cadmium
Lead-acid Battery Construction
- Consists of 6 cells for a 12-volt battery or 12 cells for a 24-volt battery.
- Containers are made from hard rubber, plastic, or other insulating material.
- Resistant to electrolyte, mechanical shock, and extreme temperatures.
- Vent plugs allow gases to escape.
Lead-acid Battery Construction - Components
- Separators hold plates apart while allowing the free movement of electrolyte.
- Separator material includes wood, perforated glass, rubber, or plastic.
- Bottom of the cell contains a space to collect sediment that forms during use.
- There is always one more negative plate than positive plates.
- All cells have an uneven number of plates, for example, a 9-plate cell has 5 negative and 4 positive plates.
Lead-acid Battery Discharging
- Sulphuric acid combines with the active material in both plates.
- Forms "lead sulphate" on the plates and water (H2O) in the electrolyte.
- Increases battery internal resistance and decreases electrolyte specific gravity (SG).
- Completely discharged SG is 1.150.
- If left discharged for a prolonged period, sulphation occurs, and the cells lose capacity.
Lead-acid Battery Charging
- Reverses the chemical action from discharging.
- Sulphate on both the positive and negative plates disassociates from lead.
- Sulphate returns to the electrolyte to form sulphuric acid (H2SO4).
- Positive plate changes back to lead peroxide, and the negative plate changes back to spongy lead.
- Specific gravity of the electrolyte rises to the charged value, approximately 1.270
Lead-acid Battery Final Charging Phase
- Little or no sulphate remains on the plates.
- Charging current decomposes water into its hydrogen and oxygen components.
- Gases are released through vent plugs; hydrogen gas is explosive.
- Batteries in service need to be periodically topped up with distilled water.
Lead-acid Battery Operation Review
- Discharging a lead acid battery below 10.5 volts will severely damage it.
Internal Resistance
- Every cell has internal resistance.
- Opposes current flow through the cell, limiting battery output.
- Inversely proportional to the area of electrodes exposed to electrochemical action.
- Directly proportional to the distance separating electrode surfaces.
- Influenced by the nature and condition of the electrolyte, typically increasing with age.
- Becomes part of the overall circuit resistance.
Nickel-Cadmium Cells
- Known as Ni-Cad, far superior to Lead-acid cells.
- Require less maintenance regarding the addition of electrolyte or water.
- Negative terminal is Cadmium.
- Positive terminal is Nickel Oxide.
- Electrolyte is Potassium Hydroxide and water (30% by weight).
Nickel-Cadmium Cell: Discharging
- When the cell is discharged:
- Negative terminal becomes Cadmium Hydroxide.
- Positive terminal becomes Nickel Hydroxide.
Nickel-Cadmium Cell
- Ni-Cad and Lead-acid cells have comparable capacities at normal discharge rates.
- At high discharge rates, Ni-Cad cells can deliver more power.
- Ni-Cad cells can:
- Be charged in a shorter time.
- Stay idle longer in any state of charge.
- Keep a full charge when stored for a longer period.
- Be charged and discharged any number of times without detriment.
Nickel-Cadmium Cell
- Nominal open-circuit cell voltage is 1.3 volts.
- Significant advantage over Lead-acid is the very low internal resistance:
- Voltage remains constant until almost totally discharged (70-80% of charge).
- Allows high charging rates without damage.
- High discharge and charging rates are favourable, but dangers are involved, particularly high battery temperatures.
Nickel-Cadmium Cell: Thermal Runaway
- High charge cycles produce high temperatures.
Connecting cells
- Batteries connected in series increase voltage but not current.
- Batteries connected in parallel increase current but not voltage.
- Batteries connected in series-parallel increase both current and voltage.
Battery Questions
- What is the purpose of a cell? A cell is a device that converts chemical energy to electrical energy.
- What are the 3 parts of a cell? Electrodes, electrolyte, and container.
-
What is the purpose of each of the 3 parts of a cell?
- Electrodes conduct current.
- Electrolyte acts upon the electrodes.
- Container holds the electrolyte and mounts the electrodes.
- What is electrochemical action? The process of converting chemical energy into electrical energy.
- What serves as the negative terminal of a dry cell? The Zinc container.
- Why is a dry cell called a DRY cell? The electrolyte is not a liquid but is in the form of a paste.
- What are the 2 types of cells? Primary and secondary.
- What is the main difference between the 2 types of cells? Secondary cells can be restored to their original condition by an electric current, while primary cells cannot.
- Can a battery be recharged by adding more electrolyte? No, a current must be passed through the battery.
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What are the 3 ways of combining cells, and what is each used for?
- Series: Increase voltage but not current.
- Parallel: Increase current but not voltage.
- Series-parallel: Increase both current and voltage.
-
What are some advantages of a Ni-Cad cell over a lead-acid cell?
- Can deliver a larger amount of power.
- Can be charged in a shorter time.
- Stays idle longer in any state of charge.
- Be charged and discharged any number of times without detriment.
-
What is used to neutralize (a) acid and (b) alkaline spills?
- Acid: Bicarbonate of soda (baking soda) or ammonia.
- Alkaline: Chromic acid solution on aircraft, 3% solution of boric acid or acetic acid (vinegar).
Battery Summary
- Capacity is an indication of a battery's current-supplying capability for a specific period, measured in ampere-hours.
- Battery charge is the process of reversing current flow through the battery to restore it to its original condition.
- Gassing is the production of hydrogen gas caused by the charge current breaking down the water in the electrolyte.
- Steady gassing is normal during the charging process. Violent gassing indicates that the charge rate is too high.
Thermocouples
- One of several devices for sensing temperature.
- Typical uses in aircraft include:
- Sensing cylinder head temperature on piston engines.
- Sensing the temperature of gas passing into, through, or from turbines (gas turbine engines).
- Some older aircraft use them as fire warning detectors, sensing abnormally rapid temperature increases.
Thermocouple Operation
- The production of EMF by heat is generated by applying heat to a junction formed by two dissimilar metals.
- The joined metal junction is the hot junction.
- The unjoined section is the cold junction.
- Applying heat to the metals results in freeing electrons.
- The energy required to free electrons differs for each metal, resulting in a varying charge.
- The potential difference between the metals can be measured at the cold junction.
- The phenomenon of producing a potential via heat is called the Seebeck effect.
- The combination of the junction and the two dissimilar metals is known as a thermocouple.
Thermocouple Operation
- The hot junction is connected to a meter calibrated in degrees Celsius.
- The meter effectively forms the cold junction.
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Description
Test your knowledge on electrolytic and galvanic cells, including their processes of oxidation and reduction. Delve into the specifics of alkaline cells and secondary cells, exploring their properties, types, and applications. This quiz will cover essential concepts to help you understand various types of electrochemical cells.