Cells Electromotive Force and Internal Resistance

Bookmark added to your notes.
View Notes
×

A cell which we have already discussed in our previous articles or an electrochemical cell is a device that can be said as it is capable of obtaining electrical energy from chemical reactions or vice versa. We have definitely seen a cell the small one is called as AAA or AA batteries we use in our remotes.


An battery or we can also say that an electric battery is a device which is made up of two or we can say more cells that make use of the chemical energy which is stored in the chemicals and converts it into energy or the electrical energy. 


Note: A battery which we often have seen in our day to day lives  is used to provide a continuous steady current source that is by the way of providing constant EMF or Electromotive force to an electrical circuit or we can say a machine.

Cells Electromotive Force Explained

Each of the cells comprises two half-cells which are connected in series by a conductive electrolyte containing cations and the anions. One of the half-cell which is made up of the electrolyte and the electrode which is negative the Anode. 

The one which is negatively charged ions also called as Anions or the migrate to the Anode. The other half-cell which generally includes the electrolyte and the electrode which is positive and the Cathode to which cations positively charged ions migrate.

How do Redox Reactions Occur?

The Redox reaction is said to be a reduction and oxidation process which occur simultaneously and this powers the battery. The Cations are reduced and it gains electrons at the cathode during charging while anions are oxidized by the process of  losing electrons at the anode during charging. During this whole process of discharge the process is reversed. The electrodes which we already do not touch each other but are electrically connected by the electrolyte.

EMF Physics Class 12

An electric power supply is also a cell or the Electric cell. The Cells generate the electricity and also derive the reaction which is the chemical reactions.  One or more cells which are electrochemical are batteries. 

Every cell that has two terminals which were namely

  • The Anode

The Anode is said to be an terminal from where the flow of current is in from out that is that it provides an incoming channel for the current to enter the circuit or the device.

  • The Cathode: 

When there is present current which is in the device or the circuit which is electrical and there’s a voltage drop also which is in source voltage or battery source which is internal resistance. It is caused due to material electrolytic in batteries or other the source voltage.


The Internal Resistance which is r = (E – V)/I


Where, E is the emf of the device that is the V which is the potential difference that is between the device the capital letter I is the current in the device. The resistance which is the Internal Resistance is the result of the resistance in the battery or we can say that the accumulation in the battery. the equation which is used to derive this is as follows equations:

V = (E – Ir).

What is a Cell in Physics?

We know that current that is electrical current is the flow of charged particles. It is the flow of electrons that take through a circuit.

A cell is said to be a device that maintains the potential difference which exists between the two electrodes that too due to chemical reaction. A collection which is of two or more cells that are connected in parallel or series is called a Battery. Thus we will obtain the voltage which is required or current.  


We know that a battery which is an energy source that converts energy which is said as the chemical energy to electrical energy. It is otherwise called a cell which is electrochemical. The energy that is stored in the form of chemical form which is  inside a battery. The Batteries give us a perfect convenient source of energy for energizing devices without wires and cables. When it is connected to a circuit it produces energy or electrical energy.


A battery consists of two terminals that is a negative and a Positive terminal. The terminal which is positive is known as Cathode and the terminal which is negative is known as Anode. They are also known as the electrodes of a Cell. These electrodes will be dipped later in the study in a solution which is known as the  electrolyte. It is liquid which is ionic and electricity which is conducted by them. The voltage which is said to be the output of a battery depends upon the elements that are used as electrodes the size which is of the electrodes and the type of electrolyte that is used in it.

FAQ (Frequently Asked Questions)

Q1. Explain What is the Internal Resistance of a Cell?

Ans: the resistance which is said as the Internal resistance refers to the opposition to the current flow offered by the batteries and cells themselves resulting in the generation of heat. the Internal resistance which is measured in Ohms laws. The relationship which is between internal resistance that is r and emf e of the cell is given by. e = I (r + R)

Q2. Explain Why a Chemical Cell has Internal Resistance?

Ans: When there is present current which is in the device or the current or the electrical and there's a drop of voltage which is in source voltage or source battery is internal resistance. It is caused especially due to electrolyte material which is in batteries or we can say other voltage sources.

Q3. Explain What is the EMF of a Cell in Physics?

Ans: The electric or the voltage potential difference which is across the terminals of a cell when no current is drawn from it. The force which is electromotive emf is the sum of the electric potential differences which is produced by a separation of charged electrons or ions that can occur at each phase boundary or we can say the interface which is  in the cell.

Q4. Explain What causes Internal Resistance?

Ans: The grid and the Sulfation corrosion are the main contributors which is to the rise of the internal resistance with acis lead. The Temperature is also affected by the resistance or we can say the heat lowers it and cold raises it. Heating which is of the battery which will lower momentarily the internal resistance which is to provide extra runtime.