Cells and Batteries Key Points

4.6 Cells and Batteries Key Points

1. An electric cell consists of two electrodes and an electrolyte.
2. Primary cells cannot be recharged, while secondary cells are rechargeable.
3. The zinc-acid cell is not commercially produced because it suffers from polarization and local action.
4. Polarization in cells is the process during which gas bubbles form on an electrode thereby insulating it from the chemical reactions of the cell.
5. Local action is the formation of local cells on the zinc electrode due to iron or lead impurities.
6. The Leclanché cell is the most commonly used wet or dry cell. It consists of a zinc cathode, a carbon anode, sal ammoniac electrolyte and a depolarizer.
7. The dry cell is manufactured in four sizes: D, C, AA and AAA.
8. The mercury cell is constructed small in size for powering small gadgets. It has a very high energy output for its size but due to its high mercury content it has been superseded by silver oxide, zinc air and lithium air cells.
9. Lithium air at the current has the highest shelf life and power output among the so called button or coin cells.
10. The e.m.f. of a cell depends on the materials of its electrodes and electrolyte.
11. Batteries consist of two or more cells connected together to supply large amounts of electric energy.
12. Cells are connected in series to achieve a higher effective voltage source.
13. Cells are connected in parallel to increase the effective current supply.