Cells and Batteries

                                 Cells and Batteries         

                            

Batteries are the source of DC electric energy, which is made available by an electrochemical system in which chemical energy is converted into electrical energy. Battery is the combination of cells which can be divided into two main categories i.e. primary and secondary cells according to the chemical action takes place in both the cells.

           Chemical Effect of Electric Current

When an electric current is passed through an electrolyte then it decomposes into its constituents and this effect is called chemical effect of electric. Some of important terms related to chemical effect of electric current are discussed below

    Electrolyte

The conduction of current through certain salt solutions is quite different from the conduction of current through the conductors. Such liquid or solutions or solutions provide oppositely charged atoms or group of atoms and are known as electrolyte e.g. , solutions of NaCl, CuSo, AgNO₃, etc.

A liquid which conducts electric due to the drifting of ions is called an electrolyte. The drifting of ions dissociation takes place in the form of anode and cathode.

    Electrode

For the flow of current in electrolyte, two metal rods are used,  they are called as electrodes. They are of two types.

(1) Anode An Anode is an electrode through which positive charge flows.   

(2) Cathode A  cathode is an electrode through which electrons enter.

    Electrolysis

When a DC current is passed through an electrolyte, then it is separated into its ions. Among them, one is positive(+)ion and other is negative(-)ion.

e.g. ,                        H₂SO₄ →  2H⁺ + SO₄^{- -}

                                CuSo₄   →  Cu⁺⁺ + SO₄^{- -}

In  first chemical reaction, sulphuric acid is separated in hydrogen(+)and sulphate (-) ions and in second chemical reaction, copper sulphate is separated in copper(+) and sulphate(-)ions.

When anode of electrode is connected to positive terminal of the battery and cathodeof electrode is connected to the negative terminal of the electrolyte due to which, positive ions mons move towards cathode and negative ions move towards anode.

In sulphuric acid, H⁺ ions give its charge to cathode and  forms hydrogen (H₂)gas and SO₄^2- ions on reaching anode, react with water and forms sulphuric acid H₂SO­­­­­­­₄ and oxygen gas(O₂)­­­.  

                              2H₂O+2SO₄^2- → 2H₂SO₄+O₂