The same considerations advanced above apply to this exemplar as well; in fact, the field created by the two coils at the centre of the magnetic needle can easily be calculated and is still directly proportional to the intensity of the current and the number of turns and inversely proportional to their radius, less a numerical constant that is evaluated exactly.
The two versions of the tangent galvanometer differ not only because the magnetic field created by the two-coil galvanometer in the region in which the needle is located is practically uniform, but also because with the same amount of current it is far more intense than that which is created by the one-coil galvanometer; the consequence is that the two-coil instrument is far more sensitive than the one-coil version.
A small magnetic needle is suspended from a thin thread having a negligible elastic moment of torsion, in the centre of a cylindrical brass box (diameter 26 cm, height 3 cm) with a glass base and cover.
A very light, thin aluminium index joined to the needle at the centre and normally directed to the axis, moves on a scale graduated from 0 to 360 degrees etched on the cover, with intervals of five degrees. ...continues