What are electro chemical cells ? How are they constructed ? Explain the working of the different types of galvanic cells ?

Explanation

Electrochemical cell is a device which makes use of a spontaneous redox reaction for the generation of electrical energy. Eg: Galvanic cell, Deniell cell etc.
Galvanic cell : A device which converts chemical energy into ele3ctrical energy by the use of spontaneous redox reaction is called Galvanic cell (or) voltaic cell. Eg: Daniell cell.
Daniell cell : It is a spacial types of glavanic cell. It contains two half cells in the same vassel. The vessel is devided into two chambers. Left chamber is filled with `ZnSO_(4)` (aq) solution and Znrod is dipped into it. Right chamber is filled with aq. `CuSO_(4)` solution and a copper rod is dipped into it. Process diaphragm acts as Salt bridge. The two half cell's are connected to external battery.
Cell reactions :
Ion `Zn//ZnSO_(4)` half cell, oxidation. reactin occurs
`Zn to Zn^(2+)+2e^(-)`
Ion `Cu//SO_(4)` half cell, reduction reaction occurs.
`Cu^(+2) +2e^(-) to Cu`
The net cell reaction is
`Zn+Cu^(+_2)hArrZn^(+2)////Cu^(2+)//Cu`
`to` The two vartical line `phi` represents a salt bridge.
`to` It is U shaped tube filled with KCl and agar agar gel slat bridge maintains the electrical neturality and flow of current.
The batteries which after their use over a period of time, becomes dead and the cell reaction is completed and this cannot be reused again are called primary batteries.
Eg: Leclanche cell, dry cell.
Second battery : A secondary battery is the battery in which after it's use can be recharged and can be uded again.
A good second battery undergoes large no. of discharging and charging cycles.
Lead storage battery is and example of second battery.
The cell reactions when the battery is in use are
`Pb_((s))+SO_(4(aq))^(-2)to PbSO_(4(s))+2e^(-) ` (Anode)
`PbO_(2(s))+ SO_(4(aq))^(-2)to 4H_((aq))^(+)+2e^(-) to PbSO_(4(s))+2H_(2)O_((l))`(Cathode)
Overall cell reaction is `Pb_((s))+ PbO_(2(s))+2H_(2) SO_(4(aq))to2PbSO_(4(s))+2H_(2)O_((l))`
In batteries also the principle invilved same as in the galvanic cell.