In the above example the force on the current l is just given by F=lB and its direction is to the left The lines of b are plotted in fig 13-2 These lines are under tension and repel each other laterally, giving rise to magnetic forces
13.2 Magnetic Pressure a current sheet carries a current density a(am pere/meter). It generates B Bv ∮B·dl=poI, taking a closed path around the current, we have B+B=0. so the magnetic field generated on both Sides of the sheet is B 0 its direction one side is upward another side is downward(both⊥toa)