ELECTROMAGNETIC FORCE CALCULATIONS FOR A CONICAL COIL

Levitation melting devices used in the laboratory typically employ sma ll conical coils with a reverse wound turn at the top. The magnetic fi eld and the Lorentz forces on an electrically conducting sample, due t o an alternating current flowing in a small conical coil, are studied by modeling it as a conical helix. These are compared with the results obtained by using the 'stack model' of the coil. The influence of the semiangle and pitch of the coil on the field and the field gradient i s studied. Further, it is shown that the stack model overestimates the field (and by extension the Lorentz force) at the bottom of the coil. The results obtained by using the stack and helix models are shown to match in the limit of vanishing pitch of the coil.