When a voltage is applied to the electrodes dipped into an electrolytic solution, ions of the electrolyte move and, therefore, electric current flows through the electrolytic solution. The power of the electrolytes to conduct electric current is termed conductance or conductivity.
(1) Ohm's law: This law states that the current flowing through a conductor is directly proportional to the potential difference across it, i.e.,
where I is the current strength (In Amperes) and V is the potential difference applied across the conductor (In Volts)
where R is the constant of proportionality and is known as resistance of the conductor. It is expressed in Ohm's and is represented as The above equation is known as Ohm's law. Ohm's law may also be stated as,
“the strength of current flowing through a conductor is directly proportional to the potential difference applied across the conductor and inversely proportional to the resistance of the conductor.”
(2) Resistance: It measures the obstruction to the flow of current.The resistance of any conductor is directly proportional to the length (l)and inversely proportional to the area of cross-section (a) so that
where (rho) is the constant of proportionality and is called specific resistance or resistivity. The resistance depends upon the nature of the material.
Units: The unit of resistance is ohm In terms of SI, base unit is equal to
(3) Resistivity or specific resistance : We know that resistance R is
; Now, if then
Thus, resistivity is defined as the resistance of a conductor of 1 cm length and having area of cross-section equal to
Units: The units of resistivity are
Its SI units are Ohm metre But quite often Ohm centimetre is also used.
(4) Conductance: It is a measure of the ease with which current flows through a conductor. It is an additive property. It is expressed as G. It is reciprocal of the resistance, i.e.,
Units: The units of conductance are reciprocal Ohm or mho. Ohm is also abbreviated as so that may be written as
According to SI system, the units of electrical conductance is Siemens, S (i.e.,
(5) Conductivity: The inverse of resistivity is called conductivity (or specific conductance). It is represented by the symbol, (Greek kappa). The IUPAC has recommended the use of term conductivity over specific conductance. It may be defined as, the conductance of a solution of 1 cm length and having 1 sq. cm as the area of cross-section. In other words, conductivity is the conductance of one centimetre cube of a solution of an electrolyte.
Units: The units of conductivity are
In SI units, l is expressed in m area of cross-section in so that the units of conductivity are