The Electromagnetic Pump 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 the 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 I is in the field (Fig). The tube is filled with a conducting liquid, and an electric current of density J is maintained in the third mutually perpendicular direction.
(a) Show that the difference of pressure between a point in the liquid on a vertical plane through ab and a point in the liquid on another vertical plane through cd, under conditions in which the liquid is prevented from flowing, is Δp= JlB.
(b) What current density is needed to provide a pressure difference of 1.00 atm between these two points if B = 2.20 T and I = 35.0 mm?

`Liquid metal or blood