Chemical effects of current
Voltmeter or coulomb meter:
The vessel in which electrolytes is carried out.It is also called electrolytic cell.
An ionic compound in aquas solution or molten state is called an electrolyte.
On passing current through an electrolyte,chemical changes occur in electrolyte and substances are liberated at the electrodes.This process is called electrolysis.
The mass of a substance liberated on electrode is proportional to the current passed through it and proportional to the time for which current is passed.
m ∝ I
and m ∝ t
Where z is called electrochemical equivalent.Since It = Q; m=ZQ
Z =Chemical equivalent in gram/1 Faraday
Faraday (F):It is the amount of charge on 1 mole of electrons =96485 C.Practically we use 1F =96500 c.
If same quantity of electricity is based through different electrolytes,the mass of the substances deposited at the respective cathodes are directly proportional to the chemical equivalent.
Note 1 Faraday of charge will liberate 1 gram equivalent any substance during electrolysis.
Electrolytic cell or voltmeter may be used to measure current more accurately than ammeters.
It is the potential difference opposite to the thermal emf setup due to accumulation of ions around the double electrodes.The back emf depends upon the nature of the electrodes and concentration of ions.