Defects In Voltaic Cell

There are two defects in voltaic cell.

1. Local action

2. Polarization

1. Local action:

➡Zinc plate contains carbon and iron particles as impurities.

➡These impurities react with acid present in the voltaic cell  and along with zinc particles to form tiny cells creating a local electric circuits known as local action.

➡Usually zinc plate are coated with Mercury to prevent this local action.

➡This Mercury prevent the impurities to come in direct contact with acid to form the local action.

2. Polarization:

➡As the  current passes through this cell, the zinc plate start dissolving in the acid to form hydrogen bubbles.

➡This hydrogen Bubbles move towards the copper plate and resist flow of current. This is known as polarization.

➡Depolarisers are used to reduce this  polarization.

➡Oxidizing agents act as depolarizer which reacts with hydrogen Bubbles and this converts into water.

➡Usually potassium dichromate, manganese dioxide, copper sulphate are used as depolarizers.