Correct Answer - C
The existence of electrical charge on colloidal particles is confirmed by the phenomenon of electrophoresis. It involves the movement of colloidal particles, either towards the electrophoresis experiment, the colloidal solution is placed in a `U`-tube fitted with platinmum electrodes. On oassing an electrode i.e. positively charged particles move towards the oppositely charged electrode i.e. positively charged particles move towards the cathode while negatively chaged particles move towards the anode. For example, if arsenious sulphide sol negatively charged is taken in the `U`-tube, its particles move towards the anode.
When electrophoresis (i.e. movement of colloidal particles) is prevented by some suitable means, it is observed that the dispersion medium begins to move in an electric field. This phenomenon is termed electro osmosis.
