Which of the following is correct about an electric cell?

Analysis of the Question

This question tests your understanding of the characteristics of electric cells, specifically the difference between primary cells and secondary cells in terms of their internal resistance and their ability to deliver current.

Concept Explanation

• Primary Cells: These are cells that cannot be recharged once they are exhausted (e.g., Leclanché cell, Daniell cell). They are generally designed for low-drain devices and typically have a high internal resistance, which limits the amount of current they can supply.
• Secondary Cells (Accumulators): These are rechargeable cells (e.g., Lead-acid accumulator, Nickel-cadmium cell). They are designed to supply large currents for extended periods. To achieve this, they are constructed with a very low internal resistance. This low resistance allows them to deliver high current without a significant drop in terminal voltage.

Step-by-Step Solution

1. Evaluate Option A: Primary cells are usually for low-current applications (like remote controls or wall clocks). They do not produce large currents for long periods. This is incorrect.
2. Evaluate Option B: Secondary cells are designed to provide high current, which is only possible if the internal resistance is low. Therefore, saying they have a "very high" internal resistance is incorrect.
3. Evaluate Option C: Primary cells typically have a high internal resistance, not a low one. This is incorrect.
4. Evaluate Option D: Because secondary cells are designed to deliver high currents (like starting a car engine), they must have a very low internal resistance to minimize energy loss within the cell and prevent overheating. This is the correct characteristic.

Conclusion

Exam Tip: Remember the "LR" rule for secondary cells: Low Resistance = Large Rechargeable current. This will help you recall that secondary cells are built for efficiency and high output!