A rectangular coil of N turns and of length a and width b is rotated at frequency b in a uniform magnetic field B, as indicated in Figure. The coil is connected to co-rotating cylinders, against which metal brushes slide to make contact.

(a) Show that the emf induced in the coil is given (as a function of time r) by ξ = 2Ï€f Nab B sin (2Ï€ft) = ξ₀sin (2Ï€ft). This is the principle of the commercial alternating-current generator.

(b) What value of Nub gives an emf with ξ₀ = 150 V when the loop is rotated at 60.0 rev/s in a uniform magnetic field of 0.500 T?

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Sliding contacts вх