Alkaline dry cells. Mercury cells

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Electric cell is a device that stores electric energy in the form of

chemical energy. All cells consist of an electrolyte (solution containing ions), positive electrode and negative electrode. Electricity is generated when the negative electrode (cathode) reacts with the electrolyte. During the reaction electrons are released. They move to the positive electrode (anode). The electric energy is released when a conductor is connected be- tween the terminals of the cell. When the cell has no power to release elec- tricity (when electrolyte has reacted fully), the cell is said to be discharged. Some types of cells can be recharged by passing current in reverse direc- tion. This type of rechargeable cells is also called storage cell or secondary cell. Primary cells cannot be recharged.

Let’s consider some basic types of electric cells.

Alkaline dry cells

One of the oldest types of primary cell used today is alkaline dry cell. This type of cell consists of a positive electrode made of manganese oxide (MnO) and a negative electrode made of zinc. The electrolyte is potassium hydroxide (KOH). Alkaline cells are widely used in radios, remote controls and

torches. They can supply quite large currents for long periods.

Mercury cells

Mercury cells are made in the shape of a small disc to be used in small portable electronic devices. They can be

used in wristwatches, calculators, etc. In these cells the negative electrode consists of zinc, while the positive electrode is made of mercuric oxide

(HgO). The electrolyte is a solution of potas- sium hydroxide (KOH).