What is an Electric Cell?
A cell is a single-unit device in which chemical energy is converted into electrical energy. It consists of some chemicals called electrolytes and has two terminals referred to as electrodes.
In a cell chemical reaction (oxidation-reduction) happens between the electrodes and the electrolyte frees more electrons in one electrode than it does in the other.
The negative terminal (called the anode) gains more electrons while the positive terminal (called the cathode) loses electrons. This exchange of electrons creates a potential difference between the electrodes that allow electricity to flow whenever connected to the outer circuit.
Battery: A battery is made up of one or more cells, each containing a positive and negative electrode immersed in a chemical solution called the electrolyte solution. So a battery can contain a large number of cells.
For example - from a single cell in an AA battery to over 7,100 cells can be packed in an 85 kWh Tesla Model S battery. Read more...
Types of Electric Cell
Based on rechargeable and non-rechargeable performance, electric cells are divided into two categories - primary cells and secondary cells.
Primary cell:
The primary cell is a type of electric cell that produces electrical energy through irreversible chemical reactions. Since the primary cell involves irreversible chemical reactions, it cannot be recharged.
This means it only converts chemical energy into electrical energy during discharging and does not have a charging system in it. Thus, primary cells are designed to be used once and then discarded.
A primary cell has a high energy density, so it drains very slowly. The terminal voltage of the primary cell is much lower than the EMF of the cell. Because the internal resistance of a primary cell is very high.
This high internal resistance causes a high voltage drop within the cell when current is drawn from it. Inside a primary cell, there is no fluid, so it is also called a dry cell.
A major advantage of primary cells is their relatively low cost. Primary cells are widely used in remote controls, watches, toys, etc.
Example: Leclanche cells and Daniel cells are examples of primary cells.
Secondary cell:
The secondary cell is a type of electric cell that produces electrical energy through reversible chemical reactions. That means while discharging it produces chemical energy into electrical energy and while charging it stores the electrical energy in the form of chemical energy.
Since the secondary cell involves reversible chemical reactions, it can be recharged. Thus, secondary cells are designed to be used repeatedly by recharging them again and again.
A secondary cell has a low energy density, so it drains very quickly. The terminal voltage of the secondary cell is almost equal to the EMF of the cell. Because the internal resistance of a secondary cell is very low.
This low internal resistance causes a very low voltage drop within the cell when current is drawn from it (while discharging). Inside the secondary cell, the electrolyte is used in liquid form, so it is also called a wet cell.
The initial cost of a secondary cell is quite more than the primary cells. But In the long term, secondary cells cost less than primary cells. Secondary cells are widely used in mobile phones, digital cameras, and many other electronic devices.
Examples: Lead-acid accumulator, Nickel-cadmium, Nickel metal hydride, Lithium-ion (Li-ion), etc are examples of secondary cells.
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