INTERNAL RESISTANCE

Internal resistance is the electrical resistance inside batteries and power supplies that can limit the potential difference that can be supplied to an external load.

                                                    [OR]

It is the resistance offered by the electrolyte of a cell to the flow of current between its electrodes.

INTERNAL RESISTANCE-IMAGE

Internal resistance of a cell is the resistance offered by the electrode and electrolyte which oppose the current flow inside the cell. The higher the internal resistance, the less current the battery is capable of giving.

                                                                                                  (OR)

Simply internal resistance is the opposition to the flow of current within the battery itself, which causes a voltage drop when current flows.

A freshly prepared cell has low internal resistance and this increases with ageing. Batteries that have high internal resistance will take more time to fully charge.

INTERNAL RESISTANCE VALUE OF A DRY CELL AND LECLANCHE CELL

High resistances cause the battery to heat up excessively and voltage output to drop under high demand. The internal resistance of a dry cell varies from about 0.5 to 1.0 ohms.The internal resistance of a  Leclanche cell is about 5 to 10 ohms.

PRACTICAL IMPORTANCE OF INTERNAL RESISTANCE OF A CELL

Internal resistance is important because it affects the battery’s efficiency, performance, and lifespan. Higher internal resistance leads to more energy loss as heat.

The concept of internal resistance is useful for analyzing many types of electrical circuits. The strength of the current obtained from a cell depends not only on the emf but also on the internal resistance. Elevated internal resistance measurements can be a sign that a cell is nearing failure.

INTERNAL RESISTANCE – FORMULA

EMF AND POTENTIAL DIFFERENCE:

DIFFERENCE BETWEEN EMF & POTENTIAL DIFFERENCE

HOW TO CALCULATE INTERNAL RESISTANCE OF A CELL/BATTERY?

Measuring Internal Resistance

Internal resistance is a critical parameter for assessing battery health and performance.

Methods of measurement

Ohm’s law

Apply a known load to the battery, measure the voltage drop and use Ohm’s law (R=V/I) to calculate resistance

AC impedance Testing

Use an AC  signal to measure the impedance(Resistance to AC) of the battery.

Specialized Equipment

Tools like battery analyzers or multimeters with internal resistance measurement capabilities.

Impact of temperature on resistance

The internal resistance of a battery is greatly impacted by temperature.

Low Temperatures:

The ions in the electrolyte travel more slowly at low temperatures, which decreases conductivity and raises internal resistance.

High Temperatures:

Conductivity improves at high temperatures because internal resistance falls. Excessive heat, however, can shorten battery life and deteriorate battery materials.

Optimal Range:

Batteries work optimally in a range of temperatures when chemical reactions are effective and internal resistance is balanced.

Day-to-Day Practical Applications of Internal Resistance of a Cell/Battery

Electronic Battery Performance

Smartphones and Laptops :

Internal resistance affects the battery life and charging speed. Higher internal resistance can lead to slower charging and reduced efficiency.

Electric Vehicles:

The internal resistance impacts the range and performance of Electric Vehicles. Lower internal resistance means better efficiency and longer range.

Power Tools:

The tool’s efficacy( Saws and Cordless Drills) may be diminished by the battery heating up due to high internal resistance.

Systems for Renewable Energy:

Solar Power Storage:

To guarantee optimal performance and lifespan, batteries with low internal resistance are recommended for solar energy storage.

Medical Equipment:

Portable Medical Equipment:

Low internal resistance batteries are necessary for the dependable operation of devices such as defibrillators and portable oxygen concentrators.

Uninterruptible Power Supplies (UPS):

Data Centers:

UPS systems use batteries with low internal resistance to ensure quick and efficient power backup.

HOW TO CALCULATE INTERNAL RESISTANCE OF A PRIMARY CELL USING POTENTIOMETER?

CIRCUIT DIAGRAM

EXPERIMENTAL SETUP

FORMULA

TABULAR COLUMN

Frequently Asked Questions (FAQs) – Internal  resistance of a cell / battery

1. What is internal resistance in a battery?
2. Why is internal resistance important?
3.  How can internal resistance be measured?
4. What factors affect internal resistance?
5. Can internal resistance be reduced?

Answers for the Frequently Asked Questions (FAQs)- Internal resistance of a cell/battery

1. Internal resistance of a cell/battery is the resistance offered by the electrode and electrolyte which oppose the current flow inside the cell. The higher the internal resistance, the less current the battery is capable of giving.

                                                                                (OR)

   Internal resistance is the opposition to the flow of current within the battery itself, which causes a voltage drop when current flows.

2. Internal resistance is important because it affects the battery’s efficiency, performance, and lifespan. Higher internal resistance leads to more energy loss as heat.

3. It can be measured using specialized equipment like a battery analyzer or by using the voltage drop method under load.

4. Factors include battery chemistry, temperature, age, and state of charge.

5. While it cannot be eliminated, using high-quality materials, proper maintenance, and optimal operating conditions can minimize it.

Conclusion

A Leclanche cell’s internal resistance is significant because it affects the overall performance of the battery or cell. When a load is connected to the cell, the internal resistance causes a voltage drop across the cell, reducing the amount of voltage available to the load, which can result in a slower response time or lower power output.

A cell’s internal resistance influences its ability to deliver current to a load. When compared to used cells, freshly prepared cells have lower internal resistance.Did you measure the internal resistance of a cell in your laboratory?