Surface charge is the electric charge present at an interface. There are many different processes which can lead to a surface being charged, including adsorption of ions, protonation/deprotonation, and the application of an external electric field. Surface charge causes a particle to emit an electric field, which causes particle repulsions and attractions, and is responsible for many colloidal properties.
Surface charge practically always appears on an object surface when it is placed into a fluid. All fluids contain ions, positive (cations) and negative (anions). These ions interact with the object surface. This interaction might lead to the adsorption of some of them on the surface. If the number of adsorbed cations exceeds the number of adsorbed anions, the surface would gain total positive electric charge.
There is another possible mechanism leading to surface charging. It is dissociation of the surface chemical group.
Read more about Surface Charge: Surface Charge Density, Interfacial Potential, Applications of Surface Charge
Famous quotes containing the words surface and/or charge:
“If the man who paints only the tree, or flower, or other surface he sees before him were an artist, the king of artists would be the photographer. It is for the artist to do something beyond this: in portrait painting to put on canvas something more than the face the model wears for that one day; to paint the man, in short, as well as his features.”
—James Mcneill Whistler (1834–1903)
“Yet I would bear my shortcomings
With meet tranquility,
But for the charge that blessed things
I’d liefer not have be.
O, doth a bird deprived of wings
Go earth-bound wilfully!”
—Thomas Hardy (1840–1928)