821.1 Faraday's law of electromagnetic induction Solution 1 Choose wire segment dI Its speed is U=la ②68 d(em=(×B)d= DBd/988B Blade emf=d(emf= BaldI=BoL s 21.1 Faraday's law of electromagnetic induction Solution 2 PO ② The magnetic flux through e the pie-shaped segment of the circle of angle 6 e2a88 B·dS=Bs=B 2 B The induced emf d o bL d8 oBL induced emf= dt 27 Solution 1: ⊗⊗⊗⊗ ⊗⊗⊗⊗ ⊗⊗⊗⊗ ⊗⊗⊗⊗ ⊗⊗⊗⊗ ⊗⊗⊗⊗ L ω B r O P §21.1 Faraday’s law of electromagnetic induction Bl l B l B l d d(emf) ( ) d d ω υ υ = = × ⋅ = r r r 2 2 1 emf d(emf) B ldl B L L o = ∫ ∫ = ω = ω d l Choose wire segment l r d Its speed is υ = lω Solution 2: The magnetic flux through the pie-shaped segment of the circle of angle θ 2 d 2 L m B S BS B θ Φ = ⋅ = = ∫ r r The induced emf d 2 d d 2 d induced emf 2 2 BL t BL t m θ ω = = Φ = §21.1 Faraday’s law of electromagnetic induction ⊗⊗⊗⊗ ⊗⊗⊗⊗ ⊗⊗⊗⊗ ⊗⊗⊗⊗ ⊗⊗⊗⊗ ⊗⊗⊗⊗ L ω B r O P θ