TWO MAJOR TYPES OF CELLS IN PHYSICS

There are two major types of cell namely:-

1. Galvanic cell
2. Electrolytic cell

GALVANIC CELL

 It's a device used to convert chemical energy into electrical energy. It consist of two electrodes in different compartments joined by a salt bridge. In this type of cells all the reduction and oxidation reactions occur spontaneously, means free energy decreases with operation of cell. Useful work is obtained by the cell. In galvanic cells anode works as negative and cathode as positive. Electrons released by oxidation process at anode go into external circuit and pass to cathode. To setup this cell, a salt bridge is used.Example of galvanic cell :- Daniel cell

Daniel cell

In this cell, Zn rod is dipped in zinc sulphate solution and Cu rod in copper sulphate solution. Both solution are connected through KCl salt bridge. when Zn to Cu occurs. Zinc atoms change to Zn2+ and electron reach at Cu electrode, where Cu2+ changes into Cu metal and this copper deposits on electode. In this redox reactions, the transfer of electrons between oxidizing and reducing agents ocurrs through the wire and thus chemical energy changes into electrical energy.

 

ELECTROLYTIC CELL

It is a device to convert electrical energy into chemical energy. Both electrodes are in the same solution. The reactions occurring in this type of cells are non-spontaneous, that is free energy increases with operation of cell. In this cell work is done on the system. In this type of cell anode is positive and cathode is negative. Electrons enter into cathode electrode from the external source and leave the cell at anode. No salt bridge is used in this cell. Example of this cell :- Dry cell

Dry cell  

It is a primary cell based on Leclanche cell invented by G. Laclanche in 1868. In a primary cell , the electrode reactions cannot be reversed by an external source of electrical energy. In this cell reaction takes place only once taht is the cell is not rechargeable.

It is generally used in torches, transisters, radios, calculators, tape recorders.etc. The potential of dry cell is apporximately 1.5 volts.