Internal Resistance Formula

Internal Resistance Formula

Internal resistance, which causes heat to be produced, is the opposition to the flow of current provided by the cells and batteries themselves. Ohms are used to measure internal resistance. Internal resistance (r) and electromotive force (e) of cells are correlated by:

e = I (r + R)

Where e stands for electromotive force, also known as EMF, I for current, R for load resistance, and r for internal cell resistance, which is measured in ohms, are present.

Rearranging the aforementioned equation yields;

Either e = V + Ir or e = IR + Ir

When the current (I) is flowing through the circuit, V in the equation above represents the potential difference (terminal) across the cell. A cell’s emf (e) is always greater than the terminal potential difference across the cell.


Science is an essential subject whose subparts include subjects like Biology, Physics, and Chemistry. Science lessons include discussions of the Internal Resistance Formula. Science is frequently perceived by students as a vast and difficult subject. The Internal Resistance Formula must be fully understood by students in order to adequately prepare for the subject. Students will benefit greatly from using Extramarks’ Internal Resistance Formula practice questions. When studying for Science exams, students should pay particular attention to practising diagrams, learning important formulas, and practising chemical reactions. They ought to include diagrams and chemical reactions in their solutions. They will enhance their responses as a result, increasing their score. Internal Resistance Formula along with its explanation is accessible on Extramarks.

The Formula of Internal Resistance

Two terminals make up a cell, one of which is positive and the other negative. The negative terminal is known as the anode, and the positive terminal is known as the cathode. In a cell, they are both electrodes. Two or more cells connected either serially or parallelly make up a battery.

The terminal of the cell is connected to a wire in order to form a closed circuit. Positive ions in the electrolyte flow from a lower to a higher potential, providing resistance to the current flow as it travels through the wire from the positive terminal of the cell to the negative terminal.

Internal Resistance Formula of a cell is:

  • based on the electrolyte makeup of the cell.
  • proportionately related to the electrolyte concentration.
  • inversely proportional to the anode and cathode areas of an electrolyte’s electrodes.
  • inversely related to the outside temperature.
  • proportional to how far apart the cathode and anode are (electrodes).

Internal Resistance of a Cell Formula

The current passing through each parallel-connected cell varies, but the potential difference between them all does not change. A battery’s internal resistance increases as more current is drawn across it over time. A brand-new battery or cell has a low internal resistance. Emf is the name for the force that drives electric charge through a circuit. It originates from a cell or battery. EMF is therefore measured in volts (V). Continuous use of the battery or cell causes it to consume electrolytes and go through chemical reactions, which lowers the concentration of ions in the cell and impedes the flow of charge through it. The internal resistance consequently grows over time.

Definition of Internal Resistance

According to Thévenin’s theorem, a real electrical power source that is a linear electric circuit can be visualised as an ideal voltage source connected in series with an impedance. The internal resistance of the source is the name given to this impedance. The measured voltage output is lower when the power source is supplying current than the no-load voltage; the difference is the voltage drop (the sum of the current and resistance) brought on by the internal resistance. Internal resistance is a concept that can be used to analyse various electrical circuit types and is applicable to all electrical sources.

A mathematical formula that can be used to determine the resistance of an object in motion is the internal resistance formula. Heat loss, friction, and other factors contribute to internal resistance, which slows or stops the movement. When designing engines and powertrains for cars or trucks, engineers frequently use the internal resistance formula, but it can also be used in a wide variety of other situations. Students can learn how Internal Resistance Formula functions by reading this article’s explanation of the formula and its calculation. 

Internal Resistance is Important to study in the Following Ways:

  • Understanding how much internal resistance a device has and how it can be reduced is crucial for increasing the efficiency of an electric motor or any other electrical device.
  • When studying the internal resistance of batteries, internal resistance is applied. Internal Resistance is a key idea in electrical engineering and can be used in a variety of projects and electrical engineering experiments.
  • When designing engines for cars, trucks, or other large vehicles, internal resistance is also crucial. Internal Resistance (IR) is a tool that can be used in Internal Combustion Engines (ICE) to increase their power and fuel efficiency.

Here are Some Important Tips to study Internal Resistance:

The idea of the internal resistance formula is applicable to a wide range of electrical and engine configurations. Before attempting more complex applications, it is best to first understand the Internal Resistance Formula in its most basic form. The relationship between voltage, current, power input, and internal resistance is illustrated by the internal resistance formula: Voltage x Current = Internal Resistance

The Internal Resistance Formula can be used for a variety of projects and experiments, but it is best to practise using the Internal Resistance Formula on simpler tasks before attempting more challenging ones. Utilize simple circuits or batteries whose internal resistance you are familiar with to put the internal resistance formula to the test. This will make it easier for students to remember how to use the Internal Resistance formula in the future. 

Although the Internal Resistance Formula can be used in a variety of contexts, it is crucial to know where and how Internal Resistance should be used. The most common applications of internal resistance formula are in electric motors and other electrical equipment, but it can also be used to examine internal resistance in batteries. Internal Resistance (IR) can be used in Internal Combustion Engines (ICE) in cars and trucks to increase engine performance and fuel efficiency. 

Physics Related Formulas
Electric Flux Formula Doppler Shift Formula
Linear Momentum Formula Energy Consumption Formula
Specific Gravity Formula Heat Rate Formula
Critical Angle Formula Latent Heat Of Fusion Formula
EMF Formula Optics Formula
Friction Formula Potential Energy Of A Spring Formula
Angular Speed Formula Propagation Constant Formula
Average Acceleration Formula Relativity Formula
Centripetal Acceleration Formula Water Pressure Formula
Doppler Effect Formula Spherical Capacitor Formula
FAQs (Frequently Asked Questions)

1. What Causes Internal Resistance?

It can be inferred that the main causes of the increase in Internal Resistance—sulfation and grid corrosion—will result in the acid. The temperature has an impact on the resistance of the heat as well; cold increases it and heat decreases it. We can infer that heating the battery will briefly reduce its internal resistance and extend its operating time.

2. What various methodologies are there for studying internal resistance? What are the uses for internal resistance?

Understanding the Internal Resistance formula, applying it to simple projects or tasks, and using it to study batteries or engines in cars or trucks are all examples of how to use the Internal Resistance formula. Although electric motors and other electrical devices use the Internal Resistance Formula most frequently, batteries can also be studied using this formula to determine internal resistance! Internal Resistance (IR) can be used in Internal Combustion Engines (ICE) in cars and trucks to increase engine performance and fuel efficiency.

3. How do I solve issues involving internal resistance using the internal resistance formula?

The Internal Resistance formula can be used to overcome Internal Resistance: Voltage x Current = Internal Resistance By entering known values and variables, the Internal Resistance = Internal Resistance formula can be used to solve Internal Resistance problems. When designing engines or powertrains for cars or trucks, internal resistance can be overcome, enhancing the engine’s performance and fuel efficiency.

4. What is Extramarks?

Extramarks is an online learning platform that focuses on the K–12, higher education, and test preparation segments and skillfully combines pedagogy and technology to enable learning anywhere, at any time. They ensure concept learning through interactive video modules on the learning app. Every concept received 360-degree coverage by the in-house team of highly qualified subject matter experts who developed these modules, providing the opportunity for immersive online learning that ensures deeper comprehension and retention during exam preparation. With the help of online learning solutions, they hope to give students the freedom to learn at their own pace and in the comfort of their own homes, wherever that may be. To engage students, they want to up the interactivity and improve the graphics and visuals. 

Their flagship product, the Learning App, which serves K–12 students as well as JEE and NEET aspirants, has amassed a devoted learner base by offering comprehensive curriculum-mapped solutions for CBSE, ICSE, and other major boards using a combination of pedagogy and technology. The Learning App offers a variety of school-based tools, including the Assessment Center, Smart Class Solutions, and Live Class Platform, to support teachers in helping students reach their full potential through engaging instruction and individualised curriculum. The Tap-Learn-Play-based Lil One by Extramarks combines technology and pedagogy in the ideal way to engage, educate, and amuse kids under the age of five. 

The educational app provides animated, interactive learning modules that make use of cutting-edge animation and graphic design techniques. They use a three-pronged strategy of Learn-Practice-Test to make their app the best online learning platform that helps students with their studies and exam preparation. Through the Learning App, top academic authorities from across the country provide live classes for major boards like CBSE and ICSE as well as competitive exams like JEE and NEET, they are renowned for their curriculum-mapped learning modules. They provide NCERT Solutions for all classes and subjects to help students with their homework. The online learning app provides students with an infinite supply of study materials to aid in exam preparation. In-depth intelligence-backed reports are created by Extramarks – The Learning App to support students in their knowledge gap.