Page 70 - Electrician - TT (Volume 1)

ELECTRICIAN - CITS

Working
When the cell is working Ammonium chloride react with zinc, form zinc chloride, and thus liberates ammonium
gas and hydrogen ions(H ).
+
The chemical reaction outside the porous pot is as follows;
Zn + 2NH Cl ZnCl + 2NH + 2H ++
3
2
4
(zinc) +(ammonium Chloride) (zinc Chloride) + (ammonium gas) + (hydrogen ionized)
Ammonia gas is insoluble in water. When the water becomes saturated with ammonia, the gas is given off and
can be detected by its smell. The hydrogen which passes through the porous pot reacts with the MnO and is
2
converted in to water (H O) taking oxygen from MnO .
2
2
The chemical reaction inside the porous pot is;
2MnO + H2 Mn O + H O
2
2 3 2
(Manganese Dioxide) + (hydrogen) (Manganese peroxide) +(water)
This cell polarisation is removed but not complete because the hydrogen is liberated at quicker rate than the
action of depolariser. Here, some hydrogen gas gets accumulated around the carbon rod. If a little rest is given to
the cell, it becomes depolarised and cell return to its normal condition. EMF of the cell is 1.45 V, internal resistance
is varying frome1-5 ohm. The cell is used for intermittent current as required in electrical bells, telephone …

Advantages
• It is very cheap as only ammonium chloride is to be changed occasionally.
• There is only one kind of solution and hence no diffusion take place.
Disadvantages

• It is not portable
• It is cannot use for constant long service.
Construction of lead acid cell
Lead acid cell consists of the following parts.
Container

Plates
Separators
Post terminals
Container

It is made of hard Rubber(ebonite), vulcanised rubber, plastic, ceramics, and glass. Container is used to
accommodate the battery plates, separators and electrolyte. The plates rest on ribs provided at the bottom of the
container. The space between ribs is known as sediment chamber. For each cell separate partition are provided
in the container.

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CITS : Power - Electrician & Wireman - Lesson 13-19 CITS : Power - Electrician & Wireman - Lesson 13-19