Question

Which of the following is not a secondary cell ?

• A. Leclanche cell
• B. Lead storage cell
• C. Mercury cell
• D. Nickel-cadmium cell

Answer 1

Answer:

A. Leclanche cell

Classification of Electrochemical Cells

• Primary Cells: These are non-rechargeable cells. Once the chemical energy is exhausted, they cannot be restored to their original state by external electrical energy. Examples include Dry Cell (Leclanché cell), Mercury cell, and Alkaline cell.
• Secondary Cells: These are rechargeable cells. They can be restored to their original state by passing an electric current in the opposite direction to the discharge current (a process known as recharging). Examples include Lead-acid storage battery, Nickel-Cadmium (Ni-Cd) cell, and Lithium-ion (Li-ion) battery.

Key Differences for Exams

1. Reversibility: Secondary cells involve reversible chemical reactions, whereas primary cells involve irreversible reactions.
2. Usage: Primary cells are commonly used in low-drain devices like remote controls and wall clocks. Secondary cells are used in high-drain devices such as smartphones, laptops, and electric vehicles.
3. Cost and Maintenance: Secondary cells have a higher initial cost but are more cost-effective over a long period due to their reusability.

Note: A standard Dry Cell is a classic example of a primary cell frequently tested in competitive examinations because it cannot be recharged.