Which of the following is a secondary cell?

Lead storage battery

The correct option is: 3. Lead storage battery

A secondary cell, also known as a rechargeable cell or accumulator, is a type of electrochemical cell that can be recharged and reused multiple times. It can undergo reversible electrochemical reactions, allowing it to be charged and discharged repeatedly.

Options 1 and 2 are not secondary cells:

1. Leclanché cell: The Leclanché cell is a primary cell, meaning it is non-rechargeable. It is commonly used in applications where a relatively low-cost, non-rechargeable battery is required, such as in flashlights and toys.
2. Concentration cell: The concentration cell is not a secondary cell either. It is a type of electrochemical cell that relies on the difference in concentration of the same electrolyte between its two half-cells to generate an electromotive force (emf). Concentration cells can be used to measure the potential difference between solutions of different concentrations, but they are not rechargeable or suitable for repeated use like secondary cells.

Option 3, Lead storage battery: The lead storage battery, also known as the lead-acid battery, is a classic example of a secondary cell. It is widely used as a rechargeable battery in various applications, including automotive batteries, uninterruptible power supply (UPS) systems, and renewable energy storage. It can be recharged by passing an electric current through it in the opposite direction of discharge, thereby restoring its chemical constituents and allowing it to be used again.

Therefore, the correct answer is option 3: Lead storage battery.