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www.GOALias.blogspot.comElectromagneticInductionWhen the induced emf is non-zero, the current I is (in magnitude)Bl vI =r(b)FIGURE 6.12The force required to keep the arm PQ in constant motion is I lB. Itsdirection is to the left. In magnitude2 2BlvF =r0 ≤ x < b= 0 b ≤ x < 2bThe Joule heating loss is2= I rPJ2 2 2Blv= 0 ≤ x < br= 0 b ≤ x < 2bOne obtains similar expressions for the inward motion from x = 2b tox = 0. One can appreciate the whole process by examining the sketchof various quantities displayed in Fig. 6.12(b).EXAMPLE 6.8217