Example 10.8 Application: The Toroidal Transformer A widely used transformer in high-quality audio and test
equipment is built around a toroidal core, as in Figure 10.14. The transformer shown is designed to supply 48 V at 2 A
for the output stage of an amplifier. The toroidal core has a cross-sectional area of S ¼ 400 mm2, a mean magnetic path
of l ¼ 200 mm, and the relative permeability of the core is infinite. The primary operates at 240 V, 60 Hz. If the
primary coil must have 800 turns to generate the required flux in the core, calculate:
(a) The number of turns in the secondary and current in the primary.
(b) Show that the result in (a) remains unchanged if the permeability of the core is finite, as long as all flux remains
contained within the core.