Dry cells are the most common type of battery used in everyday devices, such as flashlights, radios, and clocks. They are also known as zinc-carbon batteries or Leclanché cells. Dry cells are relatively inexpensive and easy to produce, which is why they are so widely used.
Construction of a Dry Cell
A dry cell is made up of the following components:
- Zinc container: The zinc container acts as the negative electrode of the battery. It is made of thin zinc metal and is coated with a layer of ammonium chloride to prevent corrosion.
- Carbon rod: The carbon rod acts as the positive electrode of the battery. It is made of a mixture of graphite and carbon powder.
- Electrolyte paste: The electrolyte paste is a mixture of ammonium chloride and zinc chloride. It is placed between the zinc container and the carbon rod.
Working Principle of a Dry Cell
When the circuit is closed, the following chemical reactions take place inside the dry cell:
- Zinc atoms from the zinc container are oxidized to form zinc ions:”Zn(s) → Zn²⁺(aq) + 2e⁻”
- Ammonia ions from the electrolyte paste are reduced to form ammonia gas and hydrogen gas:”2NH₄⁺(aq) + 2e⁻ → 2NH₃(g) + H₂(g)”
- The zinc ions react with the chloride ions from the electrolyte paste to form zinc chloride:”Zn²⁺(aq) + 2Cl⁻(aq) → ZnCl₂(aq)”
The electrons that are released in the first reaction flow through the external circuit to the carbon rod. This flow of electrons is what creates the electric current.
Types of Dry Cells
There are two main types of dry cells:
- Standard dry cells: Standard dry cells are the most common type of dry cell. They are used in a wide variety of applications, such as flashlights, radios, and clocks.
- Heavy-duty dry cells: Heavy-duty dry cells are designed for applications that require more power, such as lanterns and power tools.
Applications of Dry Cells
Dry cells are used in a wide variety of applications, including:
- Smoke detectors
- Carbon monoxide detectors