821.1 Faraday's law of electromagnetic induction According to the definition of the emf emf= inside) or emf= YL (vx B).d/ Does the lorentz force do work? A,>0AF,<0 B d s 21.1 Faraday's law of electromagnetic induction Example 1: A metal rod of length l is rotated at angular speed a about an end in a uniform magnetic field B, as shown in Figure. Find the absolute value of the induced emf and indicated which end of the rod is at the higher electric potential 8/88 ⑧⑧ ② B 66 y x × B r × × × + + − d c ∫ + − = ⋅ = （inside） emf E dl K r r ∫ + − × ⋅ （inside ） (v B) dl r r r v B l L r r r emf = ( × )⋅d ∫ or According to the definition of the emf §21.1 Faraday’s law of electromagnetic induction > 0 Fm A ′ < 0 Fm A = 0 Fm A Does the Lorentz force do work? v r ' v r V Fm r ' Fm Fm r Example 1: A metal rod of length L is rotated at angular speed about an end in a uniform magnetic field , as shown in Figure. Find the absolute value of the induced emf and indicated which end of the rod is at the higher electric potential. ω B r ⊗⊗⊗⊗ ⊗⊗⊗⊗ ⊗⊗⊗⊗ ⊗⊗⊗⊗ ⊗⊗⊗⊗ ⊗⊗⊗⊗ L ω B r §21.1 Faraday’s law of electromagnetic induction