A toroid is a solenoid-like coil bent into a circle (Fig. 26.52a). Toroids are the configuration of choice in magnetic-confinement nuclear fusion experiments, which, if successful, could provide us with an almost unlimited energy source using deuterium fuel extracted from seawater.

The ITER consortium, an international collaboration, is building a large toroidal fusion experiment in France; it?s expected to be the first fusion device to produce energy on a large scale. Figure 26.52b shows a cross section of a toroid, with current emerging from the page at the inner edge and descending at the outer edge. The black circle is an Amperian loop

The toroid has inner radius Rin and outer radius Rout , while r is the radial coordinate measured from the center. The toroid is made from wire wound into a total of N turns, and carries current I. Which of the following is the correct formula for the magnetic field within the coils?a. B = ?₀NIb. B = ?₀NI/2??R_inc. B = ?₀NI/2??R_outd. B = ?₀NI/2?r

Transcribed Image Text:

Ampèrian loop Rin Rout Iout lin Rin Rout (b) (а) FIGURE 26.52 Diagram of (a) a toroidal coil and (b) a cross section of the coil (Passage Problems 88–91)