Transport number : According to Faraday's 1st law of electrolysis, the number of ions discharged at an electrode is proportional to the total quantity of electricity passed through the solution, hence it follows that 
Total quantity of electricity that passes through the solution a sum of the mobilities of the ions.
The quantity of electricity carried by a particular ion a the mobility of that particular ion
Thus the fraction of the total current carried by each ion is called its transport number
						

							
Dear student 
The ionic mobility (μ) is defined as the velocity attained by an ion moving through a gas under unit electric field.
Ionic mobility or Ionic conductance is the conductivity of a solution containing 1 g ion, at infinite dilution, when two sufficiently large electrodes are placed 1 cm apart.
Ionic mobilities ( λa or λc) ∝ speeds of ions (ua or uc)
Unit of ionic mobility is Ohm–1 cm2 or V–1S-1cm2
Ionic mobility and transport number are related as,
λa or λc = ta or tc × λ ∞
Absolute ionic mobilityis the mobility with which the ion moves under unit potential gradient. It's unit is cm sec–1.
Absolute ionic mobility = Ionic mobility/96,500