Faraday's Second law of electrolysis:

The mass of variant substances evolved/deposited through the passage of similar quantity of electricity are proportional to their chemical equivalence.

m  ∝  M_r/n = Equivalent weight of substance

whereas m is the mass of the substance liberated or deposited, M_r is the molar mass of the substance liberated/deposited and n is the valency number of ions of the substance (electrons transferred per ion).

If m₁ and m₂ are the mass of two variant substances liberated through the passage of similar amount of electricity and M₁ and M₂   are their respective molar masses and n₁ and n₂ are their respective valence number of ions, then

m₁n₁/M₁ = m₂n₂/M₂

For instance, let us consider the passage of electricity by solutions of CuSO₄ and AgNO₃ linked in series, so in which the similar amount of electricity is passed by them, then from the second law, we get

Mass of copper deposited × 2/ Molar mass of copper = Mass of silver deposited ×1/Molar mass of silver

The quantity of electricity or charge (Q) is equivalent to the product of current strength or charge and time for that the current is passed.

Q = current × time = I × t

The practical unit of electricity is coulomb.

where a current of 2 ampere flows for ten seconds and a quantity of electricity (Q) in coulombs is, current in amperes (I) multiplied through the time in seconds (t).

Q = ampere (I) × seconds (t) = 2 × 10 = 20 C.

For a variable current I, the electricity