The streaming potential is among the most convenient techniques
for assessing the charge properties of the pore surfaces
of porous media. When a pressure gradient is applied through a
charged porous medium, the charges in the mobile part of the
electrical double layer are carried toward the low pressure-side
resulting in an electrical current in the direction of the flow, called
the streaming current. The accumulation of charge at one end
sets up an electric field which causes a conduction current in the
opposite direction of the streaming current. When the conduction
current equals the streaming current, a steady state is achieved.