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There are two types of cells; primary cells and secondary cells.
Primary Cells
This type of cell uses a chemical reaction which converts stored chemical energy into electrical energy in a process that cannot be reversed. These cells can only be used once and are discarded after use. Examples of these are non rechargeable duracell batteries
Description of a cell
All cells have two electrodes, a positive electrode and a negative electrode. Conventional current leaves the positive electrode, flows through the external circuit and enters the negative electrode. The circuit is completed inside the cell by the movement of charge carriers in the fluid between the electrodes. This fluid is referred to as the electrolyte
The Zinc-Carbon Cell
Zinc case forms the negative electrode
Paste of ammonium chloride solution forms the electrolyte
Carbon rod forms the positive electrode
Manganese (iv) dioxide stops polarisation mixed with carbon which enlarges the positive electrode and decreases the internal resistance.
Secondary Cells (Wet cells)
These types of cells are know as storage cells or accumulators. By means of a chemical reaction, they store or accumulate the energy fed into them during a charging process. The cell gives out energy when this chemical reaction is reversed during a discharging process. An example of this is the battery used in a vehicle.
Charging a secondary cell
The cell is charged by passing electricity through it. A direct current (d.c.) is used to charge the secondary cell. The positive terminal of the d.c supply is connected to the positive terminal of the accumulator or cell. The e.m.f (or voltage) of the d.c supply must be greater than the emf of the cell to be charged.
Note that both secondary and primary cells convert chemical energy (through the chemical reaction) to electrical energy.
Comparison Primary and Secondary
General
Detailed
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