Dry Cell

4.2.2.2 Dry Cell

The dry Leclanché cell or simply dry cell is useful because it is compact and portable. It is constructed with the same materials as the wet cell, except that the electrolyte is in the form of a paste or jelly. The zinc electrode is in the form of a can, as shown below. 

Dry cell

The chemical action is the same as in the wet cell and its e.m.f. is 1.5 V, too.

Leclanché cell

4.2.2 Leclanché cell

The most common type of primary cell in use is the Leclanché cell. In its wet form, it consists of a glass jar containing:

1. a saturated solution of sal ammoniac (ammonium chloride) as the electrolyte,
2. a zinc rod as the negative electrode, and
3. a plate of carbon as the positive electrode.

4.2.2.1 Wet Leclanché Cell

Wet Leclanché cell

A mixture of manganese dioxide and powdered carbon is pressed around the carbon rod and then enclosed in a porous pot which the solution can soak through. The manganese dioxide acts as the depolarizer, while the powdered carbon gives greater conductivity.

The e.m.f. of the Leclanché cell is 1.5 V and the internal resistance of a normal size cell is 1 Ohm. The wet cells are now going obsolete.  They were once a majorly used to supply power to land-line telephone installations in remote areas.