area of cross section वाक्य

In electromagnetism, "'current density "'is the electric current per unit area of cross section.
From the equation of continuity it is evident that for area of cross section being constant, discharge is maximum when the velocity of discharge is maximum . and from Ch�zy formula and Manning formula for a certain value of slope and surface roughness velocity is maximum when the hydraulic radius is maximum . and if we take area as constant hydraulic radius is maximum if the wetted perimeter is minimum.