Physically, in a three phase winding a positive sequence set of currents produces a normal rotating field, a negative sequence set produces a field with the opposite rotation, and the zero sequence set produces a field that oscillates but does not rotate between phase windings.
32.
In the presence of a rotating magnetic field more protons flip from S _ z = + \ hbar / 2 to S _ z =-\ hbar / 2 than flip the other way, causing absorption of microwave or radio-wave radiation ( from the rotating field ).
33.
Equation ( 18 ) shows that for all positions \ overrightarrow { r } the time averaged velocity is in the direction toward the origin ( concentrating the particles towards the origin ), with speed proportional to the mobility coefficient k, the strength of the rotating field E and the strength of the perturbing quadrupole field dE _ q.
