The term Electrophoresis means Electro=electric field + Phoresis=migration. So as the name indicates,“electrophoresis is a method of separation where in charged molecules migrate in differential speeds in an applied electric field.“The charged molecules under the influence of electric field migrate towards oppositely charged electrodes.Those molecules with +ve charge move towards cathode and -ve molecules move towards Anode. The migration is due to charge on the molecules and potential applied across the electrodes.
The sample under test is placed at one end of the paper near one of electrodes. When electricity is applied, the molecules start moving to respective electrodes.But the movement is influenced by molecular weight of the molecule. So when a mixture is placed on the electrophoresis paper or agarose gel, different bands are seen along the paper after the process.This is due to differential rate of movement by molecules based on their weight.Those molecules with higher molecular weight move slower. While those with small weight move faster. Also the size of the molecule also influences the movement. The bigger size molecule experience more friction than smaller ones in motion. These molecules migrate at different speed and to different lengths based on their charge, mass and shape.