The coil of an electromagnet consists of a large number of layers of thin wire wound on a cylindrical core. The inner radius of the windings is R ₁ and the outer radius is R ₂ . The number of turns in each layer is n per meter (along the length of the cylinder), and the number of layers is m per meter in the radial direction. The current in the turns of wire is /. Find formlas for the magnetic field in the region r 1 2 .

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