A dry Leclanché cell works on the principle of chemical reaction. The cell consists of a zinc can, which acts as the negative electrode, a central carbon rod, which acts as the positive electrode, and a porous pot that houses the electrolyte. The electrolyte is formed of ammonium chloride and manganese dioxide.
When the cell is in use, the ammonium chloride reacts with the zinc can to form zinc chloride and ammonia gas, liberating electrons. The zinc chloride then dissolves in the electrolyte and reacts with the manganese dioxide to form zinc oxide and manganese chloride. This reaction also generates electrons.
These electron transfers result in the flow of electrons from the negative to the positive electrode, which creates an electrical current. The emf (electromotive force) of the cell is determined by the difference in potential between the two electrodes.
Therefore, the chemical reactions taking place within a dry Leclanché cell results in the generation of an emf or electrical potential difference between the electrodes, which allows the cell to produce an electrical current.