Let x be a any physical quantity then ∂x is said to be say error in the present quantity x.or we can also say that ∂x is error which is known as Approximation Error. Now
Diamagnetic substances are those which placed in an external magnetic field become weekly magnetized in a direction opposite to the magnetic field direction. So, Diamagnetic material possesses a small value of negative susceptibility which is independent of temperature.
Let us consider the case of single electron of charge e moving in circular orbit in an atom so the equivalent current of a single electron will be
I = ev
V is the angular frequency of electron motion.