Magnetic forces acting on conducting fluids provide a convenient means of pumping these fluids. For example, this method can be used to pump blood without damage to the cells that can be caused by a mechanical pump. A horizontal tube with rectangular cross section (height `h`, width `W`) is placed at right angles to a uniform magnetic field with magnitude `B` so that a length `l` is in the field (see figure). The tube is filled with conducting liquid and an electric current density `J` is maintained in the third mutually perpendicular direction.
Which of the following statement is true ?

Options

A. Pressure difference depends of the density of the liquid.
B. Pressure difference is independent of the dimension of the tube.
C. Pressure difference depends on the length of the liquid column.
D. Pressure difference is independent of the current density.