Which of the following has the lowest internal resistance when new?

Analysis

The question asks us to identify which of the listed electrochemical cells possesses the lowest internal resistance when it is brand new. Internal resistance is the opposition to the flow of current offered by the cells and batteries themselves.

Concept Explanation

The internal resistance of a cell depends on its chemical construction, the surface area of the electrodes, and the distance between them.

• Primary Cells (Leclanche, Daniell, Torch/Dry cells): These are designed for low-drain or intermittent use. They typically have higher internal resistance because they rely on chemical reactions that are not optimized for high-current discharge.
• Secondary Cells (Accumulators/Lead-Acid batteries): These are designed to deliver high currents (like starting a car engine). To achieve this, they are constructed with large plate surface areas and a highly conductive electrolyte (sulfuric acid), which inherently results in a very low internal resistance.

Step-by-Step Solution

1. Leclanche cell: Known for high internal resistance due to the porous pot and the nature of the electrolyte used.
2. Daniell cell: Also has significant internal resistance due to the porous partition required to separate the two electrolytes.
3. Torch battery (Dry cell): While convenient, it has a relatively high internal resistance compared to secondary cells, which is why it "runs down" quickly when used in high-drain devices.
4. Accumulator (Lead-Acid battery): This is a secondary cell. Because it is designed to provide large bursts of energy (high current), its design minimizes internal resistance to prevent energy loss as heat within the battery during discharge.

Comparing these, the accumulator is specifically engineered to have the lowest internal resistance to facilitate high-current output.

Conclusion

The accumulator (lead-acid battery) is the correct choice because its design allows for the rapid flow of ions, which corresponds to low internal resistance.

Exam Tip: Whenever you see a question comparing primary cells (like Leclanche or Daniell) to secondary cells (like Accumulators) regarding current capacity or internal resistance, always remember that secondary cells are built for high performance and lower resistance.