The toroid of FIGURE P29.55 is a coil of wire wrapped around a doughnut-shaped ring (a torus). Toroidal magnetic fields are used to confine fusion plasmas.

a. From symmetry, what must be the shape of the magnetic field in this toroid? Explain.b. Consider a toroid with N closely spaced turns carrying current I. Use Ampère??s law to find an expression for the magnetic field strength at a point inside the torus at distance r from the axis.c. Is a toroidal magnetic field a uniform field? Explain.

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N turns Axis FIGURE P29.55