APPARATUS Laplace law Appt works without mercury. The study of lorentz's force is a crucial topic of introductory physics courses and interaction between electric currents & magnetic fields is a major issue of electromagnetism. Supplied w/o power supply. Biot Savart law is similar to Coulomb's law in electrostatic & is applicable for very small conductors too which carry current. * We can use Biot Savart law to calculate magnetic responses even at atomic or molecular level.