While giving labelled diagram of dry cell write reactions taking place at cathode and anode.

Explanation

Primary cells are those in which the electrode reactions cannot be reversed by an external electric energy source . In these cells , the reaction occurs only are not chargeable .
(a) Dry cell . The dry cell was invented by G. leclanche .It consists of zinc cylinder . this is filled with a paste of `NH_4 Cl` and little of `ZnCl_2` in the form of paste in water . the zinc cylinder acts as anode the cathode is carbon rod . the carbon rod is surrounded by a black paste of magnetic dioxide `(MnO_2)` and carbon powder
when the cell is openating zinc loses electrons and `Zn^(2+)` ions dissolve in the electrolyte . the electron pass around the external circuit and are taken up at cathode this causes discharge circuit and are taken up at cathode this causes discharge of `NH_(4)^(+)` ions from the electronlyte
the reaction occrring at the electrons are given below
At anode
` Zn to zn^(2+) + 2E^(-)`
at cathode
`2NH_4^(+) (aq) + 2MnO_2(s) +2e^(-) to Mn_2 O_3(s) +NH_3 +H_2 O`
it gives a voltage of about 1.5 V
(b ) uses . the dry cells are used in torches , toys flash lighters calculators , tape - recorders and in many other devices .