Ohm’s Law and Related Terms

Electrolytic solution contains ions. When electrode potential is applied across the solution, there occurs two observations

(i) flow of current through the solution.

(ii) Chemical change resulting in liberation of dissolution of elections (electrolysis).

By ohm law, there is a relation between electrode potential applied and chemical change. Current flowing through electrolytic solution is proportional to electric field or potential applied across the solution. And current is inversely proportional to resistance offered by solution. So,

I ∝ V and or

I = constant V/R

By appropriate choice of unit Constant =1 and I = V/R. This equation can also be written as

V = IR

Here V is voltage with unit “volt”, I is current with unit “ampere” and R is resistance with unit “ohm and Ω”.

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Conductance: Denoted as 'L' is the reciprocal of resistance. L= 1/R. Its unit is ohm^-.Ω^-

Resistance depends on

i. distance between electrode R ∝ I

ii. Area of cross section of electrode R ∝ 1/A

So, and
Here ρ = resistivity or specific resistance. If l= 1m and A = 1m² then R= ρ. It is the resistance of an electrolytic solution placed between two electrodes 1m apart and having a cross section of 1m². Another term is the “specific resistance”. It is resistance of 1m³ of an electrolyte.

Specific conductance: denoted as “Ls”. Specific conductance is the conductance of a solution plated between two electrodes which are 1m apart and having a cross section area of 1m². Thus conductance of 1m³ of an electrolytic solution is specific conductance.

L = 1/R and so,

Here 1/ρ= Ls . so, Or

Unit: unit of specific conductance is sm^-1 (s=Siemen) or Ω^-m^- or mohm-¹

Cell constant:

For this given equation , A and l is known. This A/l is known as cell constant and is equal to L/Ls. Cell constant of all the conductors is known.