Discussion Examples for Battery Fabrication Experiments | Electromotive Force, Internal Resistance, and the Effect of Concentration

What Is a Battery Fabrication Experiment?

A battery fabrication experiment is an experiment in which a device that extracts electrical energy using redox reactions is constructed and the properties of its voltage and current are investigated.
When two types of electrodes and electrolyte solutions are combined, an oxidation reaction occurs at one electrode and a reduction reaction occurs at the other.
This causes electrons to flow through an external circuit and generates a voltage.

The electromotive force of a battery changes depending on the electrode materials, metal-ion concentrations, temperature, solution composition, and other factors.
The terminal voltage measured experimentally is often lower than the theoretical electromotive force, and possible causes include internal resistance, polarization, contact resistance, and changes in concentration.
In a battery fabrication experiment, it is important to carefully discuss the difference between theory and the measured value.

Main Items to Include in the Results

In the results of a battery fabrication experiment, organize the types of electrodes, types and concentrations of electrolyte solutions, presence or absence of a salt bridge, measured electromotive force, voltage when a load is connected, changes over time, changes in the electrode surfaces, comparison with theoretical values, and other information.
Because battery voltage is sensitive to conditions, it is important to clearly state the concentrations and connection method.

Main Items to Include in the Results

• Types of electrodes used
• Pretreatment of the electrode surfaces
• Types of electrolyte solutions
• Metal-ion concentrations
• Type of salt bridge or separator
• Battery combination
• Anode and cathode
• Electrode reaction equations
• Overall reaction equation
• Measured electromotive force
• Theoretical electromotive force
• Voltage when a load is connected
• Change in voltage over time
• Changes in electrode surfaces
• Effect of internal resistance
• Effect of concentration
• Causes of error and points for improvement

Reference Experimental Values and Calculation Examples for Battery Fabrication Experiments

Here, a simple battery is constructed using metal electrodes and electrolyte solutions, and the electromotive force, voltage under load, current, internal resistance, and effect of electrolyte concentration are organized using reference experimental values.

In a battery, an easily oxidized metal releases electrons and a reduction reaction proceeds at another electrode, causing current to flow.
The open-circuit voltage provides an indication of the potential difference inherently possessed by the battery, but when a load is connected and current flows, the terminal voltage decreases because of internal resistance and delays in the reaction.

Reference Experimental Conditions

Concept of Electrode Reactions

In a battery using zinc and copper, zinc is oxidized and releases electrons, while a reduction reaction occurs on the copper side.
Electrons move through the external circuit from the negative electrode to the positive electrode, and this flow can be used as electric current.

Open-Circuit Voltage and Measurement Results Under Load

First, the open-circuit voltage is measured without connecting a load, and then the terminal voltage is measured when a resistor is connected and current flows.

Example Calculation of Current

The current when a load resistor is connected is determined using Ohm’s law.

Current I = Voltage V ÷ Resistance R

For example, when a 50 Ω resistor is connected and the measured voltage is 0.89 V, the current is calculated as follows.

I = 0.89 V ÷ 50 Ω = 0.0178 A

Therefore, under the condition where a 50 Ω load was connected, a current of approximately 17.8 mA flowed.

Example Calculation of Output

The electric power supplied by the battery to the external circuit is determined from the product of voltage and current.

Output P = Voltage V × Current I

Under the 50 Ω condition, the voltage is 0.89 V and the current is 0.0178 A, so the output is calculated as follows.

P = 0.89 V × 0.0178 A = 0.0158 W

Under this condition, approximately 0.0158 W of electric power was considered to have been extracted to the external circuit.

Example Calculation of Internal Resistance

Because a battery has internal resistance, when current flows, the terminal voltage becomes lower than the open-circuit voltage.
If the open-circuit voltage is E, the voltage under load is V, and the current is I, the internal resistance r can be estimated as follows.

Internal resistance r = (E − V) ÷ I

Under the 50 Ω condition, the open-circuit voltage E is 1.05 V, the voltage under load V is 0.89 V, and the current I is 0.0178 A.

r = (1.05 − 0.89) ÷ 0.0178 = 9.0 Ω

Therefore, the internal resistance estimated from this condition is approximately 9.0 Ω.
In practice, internal resistance may change depending on the current, electrode-surface condition, electrolyte concentration, and progress of the reaction.

Relationship Between Load Resistance and Voltage Drop

As the load resistance becomes smaller, the current increases, but the terminal voltage decreases.
This is because resistance loss inside the battery and delays in the electrode reactions become greater.

Example Calculation of Voltage-Drop Percentage

The voltage-drop percentage expresses, as a percentage, how much the voltage decreases when a load is connected relative to the open-circuit voltage.

Voltage-drop percentage (%) = (Open-circuit voltage − Voltage under load) ÷ Open-circuit voltage × 100

Under the 20 Ω condition, the open-circuit voltage is 1.05 V and the voltage under load is 0.72 V, so the calculation is as follows.

Voltage-drop percentage = (1.05 − 0.72) ÷ 1.05 × 100 = 31.4%

This result shows that when current is extracted by connecting a load, the voltage decreases considerably from the open-circuit voltage.

Measurement Results When the Electrolyte Concentration Is Changed

Next, the open-circuit voltage and voltage under load are compared when the electrolyte concentration is varied.
Here, an example is shown in which the load resistance is fixed at 50 Ω.

In this reference example, as the electrolyte concentration increases, the voltage under load and current increase, while the internal resistance decreases.
However, the change becomes smaller from 0.50 mol/L to 1.00 mol/L, indicating that the effect may level off above a certain concentration.

How to Consider the Effect of Concentration

When the electrolyte concentration is low, ions move less easily through the solution and the internal resistance becomes larger.
Therefore, the voltage drop becomes greater when a load is connected, and the current and output that can be extracted become smaller.

On the other hand, increasing the electrolyte concentration improves ionic conductivity and decreases the internal resistance.
As a result, the voltage is maintained more easily even under load, and the current and output increase.

Measurement Results When the Electrode Area Is Changed

Battery performance is also affected by electrode area.
A larger electrode area increases the area available for the reaction and may make it easier to extract current.

The open-circuit voltage does not change greatly even when the electrode area is changed.
On the other hand, the voltage under load and current increase under conditions with a larger electrode area.
This is considered to result from the larger electrode area increasing the reaction area and reducing the effects of polarization and reaction resistance.

Example of How to Write the Results

A simple battery was constructed using a zinc plate and copper plate, and the open-circuit voltage was 1.05 V.
When a 100 Ω load was connected, the terminal voltage was 0.96 V and the current was 0.0096 A.
When the load resistance was decreased, the current increased, but the terminal voltage decreased, reaching 0.52 V under the 10 Ω condition.

Under the condition where a 50 Ω load was connected, the terminal voltage was 0.89 V, the current was 0.0178 A, and the output was 0.0158 W.
When the internal resistance was estimated from the difference from the open-circuit voltage, it was approximately 9.0 Ω.
This confirmed that the battery itself contains resistance components and that a voltage drop occurs when current is extracted.

In addition, when the electrolyte concentration was increased from 0.01 mol/L to 1.00 mol/L, the voltage under load increased from 0.62 V to 0.95 V, while the internal resistance decreased from 23.4 Ω to 7.4 Ω.
From this result, increasing the electrolyte concentration was considered to improve ionic conductivity and reduce voltage losses inside the battery.

Points for Connecting the Results to the Discussion

In a discussion of a battery fabrication experiment, it is important to explain not only the magnitude of the electromotive force but also the voltage drop when a load is connected and the causes of internal resistance.

• Was there a difference between the open-circuit voltage and the voltage under load?
• When the load resistance was decreased, did the current increase and the terminal voltage decrease?
• Can the internal resistance be calculated and the voltage loss inside the battery explained?
• Did the internal resistance decrease as the electrolyte concentration increased?
• Did a larger electrode area increase the voltage under load and output?
• Could the oxide film on the electrode surface, poor contact, electrode spacing, solution concentration, or temperature have affected the results?
• Did the voltage decrease over time as the reaction proceeded?

Example Discussion

In this experiment, the open-circuit voltage of the simple battery using a zinc plate and copper plate was 1.05 V.
However, when a load was connected and current was allowed to flow, the terminal voltage decreased, reaching 0.52 V with a 10 Ω load.
This was considered to result from the presence of internal resistance in the battery, causing voltage loss when current flowed.

When the load resistance was decreased, the current increased, but the terminal voltage decreased.
This was because larger current causes greater voltage drop due to internal resistance and larger delays in the electrode reactions.
When the internal resistance was estimated from the 50 Ω condition, it was approximately 9.0 Ω, showing that internal resistance is an important factor when considering battery performance.

In addition, when the electrolyte concentration was increased, the voltage under load and output increased, while the internal resistance decreased.
Under low-electrolyte-concentration conditions, the number of ions in the solution was small and ionic conductivity was low, so the resistance inside the battery was considered to have been large.
On the other hand, at higher concentrations, ions moved more readily and the internal resistance became smaller, so the voltage was maintained more easily under load.

Furthermore, increasing the electrode area increased the voltage under load and output.
This was considered to result from the larger electrode surface area allowing the electrode reaction to proceed more readily.
However, in actual measurements, oxide films on the electrode surfaces, contact resistance at connections, electrode spacing, and the mixing state of the solution may also affect the results.
Therefore, when comparing battery performance, it is important to standardize the electrode and measurement conditions.

Summary

In a battery fabrication experiment, battery performance can be evaluated more specifically by measuring not only the open-circuit voltage but also the terminal voltage under load, current, output, and internal resistance.

In this reference example, decreasing the load resistance increased the current but decreased the terminal voltage.
In addition, the higher the electrolyte concentration, the smaller the internal resistance and the greater the voltage under load and output.
In a report, it is useful to organize and discuss the relationships among electrode reactions, internal resistance, electrolyte concentration, and electrode area.

What Is Electromotive Force?

Electromotive force is the voltage representing the ability of a battery to drive current through an external circuit.
Ideally, the voltage measured under conditions where almost no current is flowing is close to the electromotive force.
The electromotive force is determined by the potential difference between the two electrodes.

In a battery, a potential difference is generated by combining an electrode that is easily oxidized with an electrode that is easily reduced.
The greater this potential difference, the greater the electromotive force that can be obtained.
However, the voltage actually measured may be lower than the theoretical electromotive force because of the effects of internal resistance and polarization.

Electromotive force E = Electrode potential of the positive electrode – Electrode potential of the negative electrode

Concept of the Anode and Cathode

In a battery, the electrode at which oxidation occurs is called the anode, and the electrode at which reduction occurs is called the cathode.
In a metal battery, a metal that is easily ionized is readily oxidized and releases electrons, so it tends to become the anode.
The released electrons move through the external circuit to the cathode, where metal ions or other species accept electrons.

However, the signs of the anode and cathode can easily be confused between batteries and electrolysis.
In a battery, the anode where oxidation occurs is the negative electrode, and the cathode where reduction occurs is the positive electrode.
In a report, it is useful to organize the electrodes based on the definitions “oxidation occurs at the anode” and “reduction occurs at the cathode.”

Discussion of the Daniell Cell

The Daniell cell is a representative chemical cell using a zinc electrode and a copper electrode.
At the zinc electrode, Zn loses electrons and becomes Zn2+, while at the copper electrode, Cu2+ accepts electrons and is deposited as Cu.
Voltage is generated by this combination of oxidation and reduction reactions.

Zinc has a greater tendency to ionize than copper and is more easily oxidized, so it acts as the anode.
Copper ions are more readily reduced than zinc ions, so copper is deposited at the cathode.
If the zinc electrode dissolves and copper is deposited on the copper-electrode side in the experiment, the result is consistent with the electrode reactions.

Anode: Zn → Zn2+ + 2e-

Cathode: Cu2+ + 2e- → Cu

Overall: Zn + Cu2+ → Zn2+ + Cu

Standard Electrode Potentials and Electromotive Force

The standard electrode potential is a value representing the potential of an electrode reaction under standard-state conditions.
The standard electromotive force of a battery is determined by subtracting the standard electrode potential of the negative electrode from that of the positive electrode.
For example, in a Daniell cell, the difference between the potentials of Cu2+/Cu and Zn2+/Zn gives the standard electromotive force.

However, in an actual experiment, the metal-ion concentrations often differ from standard-state conditions, so the standard electromotive force and the measured value do not completely agree.
Internal resistance, polarization, and other factors also lower the measured voltage.
Standard electrode potentials are used as a reference for considering theoretical values, while deviations caused by experimental conditions are discussed separately.

E0cell = E0cathode – E0anode

Effect of Concentration on Electromotive Force

The electromotive force of a battery is affected not only by the electrode materials but also by the ion concentrations in the solution.
When the metal-ion concentration changes, the tendency of the electrode reaction to proceed changes and the electrode potential changes.
For example, the higher the Cu2+ concentration, the more readily Cu2+ is reduced, and the copper-electrode potential shifts in the noble direction.

Conversely, when the Zn2+ concentration increases, the tendency of Zn to dissolve as Zn2+ changes, and the zinc-electrode potential also changes.
This concentration dependence can be explained by the Nernst equation.
The reason the electromotive force changes when the concentration is varied in an experiment is that the electrode potentials change with concentration.

Concept of the Nernst Equation

The Nernst equation expresses how the electrode potential changes depending on ion concentration.
Under conditions other than the standard state, it is necessary to consider the concentrations of ions involved in the reaction rather than using the standard electrode potential directly.
This allows the electrode potential and electromotive force under the actual solution conditions to be considered.

For example, when the metal-ion concentration changes, the equilibrium of the reduction reaction of that metal ion changes and the electrode potential also changes.
In a concentration cell, even when the same metal electrodes are used, a potential difference arises solely because of a concentration difference.
In this way, the Nernst equation is an important equation for explaining the relationship between concentration and voltage.

E = E0 – (RT / nF) ln Q

At 25°C, it may be expressed as E = E0 – (0.0592 / n) log Q.

Discussion of Concentration Cells

A concentration cell is a battery in which a potential difference is generated even when the same metal electrodes are used because the concentrations of the solutions on the two sides are different.
Even when the electrode materials are the same, different ion concentrations result in different electrode potentials and therefore generate a voltage.
This can be explained by the Nernst equation.

In a concentration cell, the reaction proceeds in the direction that reduces the concentration difference.
On the side with the lower metal-ion concentration, the metal may more readily dissolve, while on the side with the higher concentration, the metal ions may more readily be reduced.
If the voltage increased as the concentration difference became larger in an experiment, this indicates that the concentration difference was the cause of the electromotive force.

Role of the Salt Bridge

A salt bridge connects the two half-cells ionically and prevents charge imbalance.
As the battery reaction proceeds, positive ions may increase in one solution and decrease in the other, causing charge imbalance.
Ions in the salt bridge move to cancel this charge imbalance and allow current to continue flowing.

Without a salt bridge, a small voltage may initially be produced, but the charge balance in the solutions becomes disturbed and the reaction becomes difficult to continue.
Poor contact of the salt bridge, bubbles inside it, drying, or high internal resistance may also lower the measured voltage.
The salt bridge is essential for stable operation of the battery.

What Is Internal Resistance?

Internal resistance is the resistance that arises when current flows inside a battery.
The electrolyte solution, salt bridge, electrode surfaces, contact points, and other components contribute to internal resistance.
When the internal resistance is large, a voltage drop occurs when current flows, and the terminal voltage measured externally becomes lower than the electromotive force.

When measured with a high-resistance voltmeter that allows almost no current to flow, a value close to the electromotive force is obtained.
On the other hand, when a load such as a small light bulb or resistor is connected, current flows and the voltage drop due to internal resistance becomes larger.
Therefore, the voltage under load is often lower than the open-circuit voltage.

Terminal voltage V = Electromotive force E – Voltage drop Ir due to internal resistance

Factors Affecting Internal Resistance

Internal resistance is affected by electrolyte concentration, condition of the salt bridge, distance between the electrodes, electrode area, solution temperature, contact condition, and other factors.
When the electrolyte concentration is low, there are fewer ions and the conductivity of the solution is low, so the internal resistance becomes large.
The internal resistance also becomes large if the salt bridge is thin, long, dry, or contains bubbles.

If the electrode area is small, the available reaction surface is small and the voltage drop when current is extracted may become larger.
If the electrode surface is dirty or covered with an oxide film, electron transfer and the reaction are also hindered.
The magnitude of internal resistance is strongly related to the practical output of the battery.

Effect of Polarization

Polarization is the phenomenon in which the electrode potential deviates from its equilibrium state because of electrode reactions or mass transfer when current is drawn from a battery.
When polarization occurs, the terminal voltage of the battery decreases.
Polarization is related to delays in charge transfer, decreases in reactant concentration, accumulation of products, adhesion of gases, and other factors.

For example, if a gas such as hydrogen adheres to an electrode surface, the area available for the electrode reaction decreases and the voltage may fall.
In addition, when current is continuously drawn, the ion concentration near the electrode changes and concentration polarization occurs.
If the battery voltage decreases over time, the effect of polarization should be discussed.

When the Measured Value Is Lower Than the Theoretical Value

In a battery fabrication experiment, the measured electromotive force or terminal voltage is often lower than the theoretical value.
Possible causes include internal resistance, polarization, contamination of the electrode surfaces, oxide films, concentrations different from standard-state conditions, poor salt-bridge contact, internal resistance of the voltmeter, and poor electrical connections.

In particular, a voltage measured while a load is connected is lower than the open-circuit voltage.
This is because current flows and a voltage drop occurs because of internal resistance.
When discussing the difference between the theoretical and measured values, it is important to distinguish whether the measurement was made under open-circuit conditions or with a load connected.

When the Voltage Decreases Over Time

When the battery voltage decreases over time, changes in the ion concentrations in the solution caused by the progress of the electrode reactions can be considered.
For example, in a Daniell cell, Cu2+ is consumed by reduction, while Zn2+ is produced and increases.
This reduces the driving force of the reaction and lowers the voltage.

The voltage may also decrease if reaction products or bubbles adhere to the electrode surfaces or if ion movement through the salt bridge cannot keep up.
Changes in voltage over time are important observations showing that the internal state of the battery changes as it discharges.

Effect of Electrode-Surface Condition

Battery voltage is also affected by the condition of the electrode surfaces.
If oxide films, dirt, oil, or corrosion products are present on a metal surface, the electrode reaction may become difficult and the voltage may decrease.
If the electrode surface is nonuniform, local reactions may occur and the measured value may become unstable.

Polishing and cleaning the electrode surfaces before the experiment expose fresh metal surfaces and make reproducible voltage measurements easier.
However, the surface condition may change over time even immediately after polishing.
It is important to standardize the electrode-surface pretreatment conditions.

Effect of Electrode Area

Ideally, the electromotive force itself is not directly proportional to the electrode area.
However, the larger the electrode area, the wider the surface available for reactions and the smaller the voltage drop may become when current is drawn.
In other words, electrode area is related more to output and internal resistance when current flows than to the electromotive force itself.

When the electrode area is small, the current density becomes larger and electrode polarization becomes more likely.
As a result, the voltage may decrease greatly when a load is connected.
When comparing battery performance, it is important to keep the electrode area consistent.

Electrolyte Concentration and Internal Resistance

When the electrolyte concentration is high, the number of ions in the solution increases and the solution conducts electricity more easily.
Therefore, the solution resistance becomes smaller and the voltage drop caused by internal resistance may decrease.
Conversely, when the electrolyte concentration is low, there are fewer ions and current flows less easily.

However, higher concentration does not necessarily always improve battery performance.
If the metal-ion concentration is too high, the electrode reaction and solution properties may be affected, and the deposition state or side reactions may change.
Because concentration is related to both the electromotive force and internal resistance, these effects should be discussed separately.

Effect of Temperature

Temperature affects electrode-reaction rates, ion mobility, solution resistance, and the terms in the Nernst equation.
As temperature increases, ions generally move more rapidly and the internal resistance may decrease.
The electrode-reaction rate also changes, affecting voltage stability and output.

However, increases in temperature may also cause side reactions or changes in the solution.
In experiments comparing electromotive force, it is desirable to keep the temperature constant.
If the temperatures differ, it becomes difficult to distinguish the effects of concentration and electrode materials, making temperature a source of error.

Effect of the Voltmeter

When measuring electromotive force, it is important to measure under conditions where as little current as possible flows.
If the internal resistance of the voltmeter is sufficiently high, almost no current flows from the battery and a value close to the open-circuit voltage can be measured.
However, if a measuring instrument with low internal resistance or a load is connected, current flows and the terminal voltage decreases.

Therefore, it is necessary to distinguish whether the measured value is the electromotive force or the terminal voltage under load.
When comparing with the theoretical electromotive force, it is appropriate to use a value measured under conditions close to open circuit.
The effect of the measuring instrument is one cause of a measured value being lower.

Causes of Error in Battery Fabrication Experiments

Causes of error in battery fabrication experiments include contamination of the electrode surfaces, oxide films, errors in electrolyte concentration, poor contact of the salt bridge, internal resistance, polarization, temperature differences, the effect of the voltmeter, poor electrical connections, electrode spacing, differences in electrode area, mixing of solutions, and errors in reading measured values.
Because a battery experiment combines multiple components, the condition of the entire apparatus affects the results.

Causes that lower the measured value include increased internal resistance, resistance of the salt bridge, poor electrode-surface reactions, polarization, differences in concentration conditions, and poor contact.
Causes of unstable voltage include movement of the electrodes, adhesion of bubbles, drying of the salt bridge, mixing of solutions, and loose connection terminals.
Causes of error are easier to organize when divided into electrodes, solutions, salt bridge, and measuring instruments.

When the Results Can Be Considered Good

A battery fabrication experiment can be considered to have produced good results when a voltage corresponding to the electrode combination is obtained, the reactions at the anode and cathode correspond to theory, and the voltage change when the concentration is varied does not contradict the concept of the Nernst equation.
In addition, if the voltage stabilizes when a salt bridge is used and the changes over time can be reasonably explained, the apparatus can be judged to have functioned appropriately.

The measured value does not need to agree perfectly with the theoretical value.
In experiments, some deviation is natural because of internal resistance, polarization, and differences in concentration conditions.
What is important is being able to explain the deviation from the reactions inside the battery and the measurement conditions.

Example Discussions When the Experiment Did Not Go Well

When a battery fabrication experiment does not go well, possible causes should be considered from results such as no voltage being produced, an extremely low voltage, unstable voltage, reversed polarity, or no observable voltage difference even when the concentration is changed.
Organizing the causes according to electrode connections, salt bridge, solution concentration, electrode surfaces, voltmeter polarity, and poor contact makes the discussion easier.

How to Write Points for Improvement

In a discussion of a battery fabrication experiment, writing not only the causes of error but also points for improvement makes the report easier to organize.
Points for improvement can be organized according to the electrodes, solution, salt bridge, measurement operation, and analysis method.

Improvements to the Electrodes

• Polish the electrode surfaces under the same conditions
• Remove oxide films and dirt
• Do not touch the electrodes with bare hands
• Keep the electrode areas consistent
• Fix the electrodes securely
• Ensure reliable contact with the wires

Improvements to the Solutions and Salt Bridge

• Prepare the electrolyte concentrations accurately
• Avoid mixing the solutions
• Keep the temperature constant
• Keep the salt bridge sufficiently wet
• Avoid bubbles inside the salt bridge
• Ensure that both ends of the salt bridge are in firm contact with the solutions

Improvements to the Measurement Operation

• Use a voltmeter with high internal resistance
• Check the polarity of the voltmeter
• Distinguish between open-circuit voltage and voltage under load
• Read the voltage after it has stabilized
• Record changes over time
• Perform multiple measurements and calculate the average value

Difference Between a Superficial Discussion and a Good Discussion

In a discussion of a battery fabrication experiment, simply writing that “a voltage was generated” or “the measured value was lower than the theoretical value” results in a superficial discussion.
A good discussion relates electrode reactions, electromotive force, concentration, internal resistance, polarization, and the role of the salt bridge.

Examples of Expressions That Can Be Used in Reports

The following expressions can be used when writing the results and discussion of battery fabrication experiments.
Adjust the necessary parts according to your own experimental results.

• In a battery, electrical energy is extracted by separating oxidation and reduction reactions.
• Oxidation occurs at the anode and reduction occurs at the cathode.
• The electromotive force of a battery is determined by the potential difference between the two electrodes.
• The standard electromotive force is determined from the difference between the standard electrode potentials of the positive and negative electrodes.
• The actual electromotive force is affected by metal-ion concentration.
• According to the Nernst equation, electrode potential depends on the concentrations of reactants and products.
• The salt bridge is necessary to maintain charge balance between the half-cells.
• When internal resistance is large, the terminal voltage decreases when current flows.
• Polarization may change the electrode potential and cause battery voltage to decrease over time.
• The difference between measured and theoretical values can be discussed in terms of internal resistance, polarization, concentration conditions, and electrode-surface condition.

Points to Check When Discussing Battery Fabrication Experiments

Checking the following points before writing the report makes the discussion easier to write.

• Is the principle of the battery explained using redox reactions?
• Are the anode and cathode correctly distinguished?
• Are the electrode reaction equations written?
• Is the overall reaction equation written?
• Is it explained that electromotive force is determined by the difference in electrode potentials?
• Are standard electrode potentials related to the theoretical electromotive force?
• Is the effect of concentration explained using the Nernst equation?
• Is the role of the salt bridge explained?
• Is the voltage drop caused by internal resistance considered?
• Are polarization and changes over time discussed?
• Is the difference between the measured and theoretical values explained specifically?
• Do the points for improvement correspond to the causes of error?

Summary

A battery fabrication experiment is an experiment in which electrical energy is extracted using redox reactions.
At the anode, a metal is oxidized and releases electrons, while at the cathode, metal ions or other species accept electrons and are reduced.
The potential difference between these two electrode reactions generates the electromotive force.

The electromotive force of a battery is affected not only by the electrode materials but also by the metal-ion concentrations.
Under standard-state conditions, the theoretical electromotive force can be calculated from the standard electrode potentials, but under actual concentration conditions, the Nernst equation must be considered.
In addition, the salt bridge plays an important role in preventing charge imbalance and allowing the battery reaction to continue.

In a report, rather than simply writing that “a voltage was generated,” organize and discuss the reactions at the anode and cathode, electromotive force, standard electrode potentials, the effect of concentration, the Nernst equation, the salt bridge, internal resistance, polarization, changes in voltage over time, causes of error, and points for improvement.
Battery fabrication experiments are important experiments for specifically understanding the relationship between redox reactions and electrical energy.