A toroid with a circular cross section is shown in Figure P11.2.3. It is made from cast steel with a relative permeability of 2500. The magnetic flux density in the core is 1.25 T measured at the mean diameter of the toroid.
(a) Find the current that must be supplied to the coil.
(b) Calculate the magnetic flux in the core.
(c) Now suppose a 10-mm air gap is cut across the toroid. Determine the current that must be supplied to the coil to produce the same value of magnetic flux density as in part (a). You may neglect leakage and fringing.
