A toroidal coil has a rectangular cross section, with inner radius a, outer radius a + , and height h. it carries a total of n tightly wound turns, and the cur

A toroidal coil has a rectangular cross section, with inner radius a, outer radius a + , and height h. It carries a total of N tightly wound turns, and the current is increasing at a constant rate (d1/dt = k). If w andh are both much less than a, find the electric field at a point z above the center of the toroid. [Hint: exploit the analogy between Faraday fields and magnetostatic fields?