Chapter 27 Electromagnetic Induction and faraday's law Magnetic flux(磁通量P630) B·d 2. Faraday's Law of Induction(P631 The emf induced in a circuit is equal to the rate of change of magnetic flux through the circuit d④ dt 当穿过闭合回路所围面积的磁通量发生变化时, 路中会产生感应电动势,且感应电动势正比于磁通量对 时间变化率的负值
Chapter 27 Electromagnetic Induction and Faraday’s Law = B S B d The emf induced in a circuit is equal to the rate of change of magnetic flux through the circuit: 1. Magnetic flux （磁通量P630） 2. Faraday’s Law of Induction (P631) t Φ d d = − 当穿过闭合回路所围面积的磁通量发生变化时，回 路中会产生感应电动势，且感应电动势正比于磁通量对 时间变化率的负值
Chapter 27 Electromagnetic Induction and faraday's law Discussion ◆ magnetic flux linkage(磁通链) If the loop is replaced by a closely packed coil ofn turns, the induced emfs do d B dt dt Where:V=Np Called magnetic flux linkage(磁通链)
Chapter 27 Electromagnetic Induction and Faraday’s Law Discussion If the loop is replaced by a closely packed coil of N turns， the induced emf is： t t N B d dψ d d = = − Where： ψ = N Called magnetic flux linkage（磁通链）. magnetic flux linkage（磁通链）
Chapter 27 Electromagnetic Induction and faraday's law the direction of emf(感应电动势的方向) dg dt (the minus sign) means the induced emf tends to B oppose the flux change. 1)规定回路的绕行正方向。 2)规定当回路中磁力线的方向 和所规定的回路的绕行正方向成 右手螺旋关系 ①>0
Chapter 27 Electromagnetic Induction and Faraday’s Law “-” (the minus sign) means the induced emf tends to oppose the flux change. the direction of emf (感应电动势的方向) t Φ d d = − N B L 0 1）规定回路的绕行正方向。 2）规定当回路中磁力线的方向 和所规定的回路的绕行正方向成 右手螺旋关系
Chapter 27 Electromagnetic Induction and faraday's law de=gt+dt)gt B ￠>0(B与回路成右螺旋) d④ >0E<O ￡与回路取向相反
Chapter 27 Electromagnetic Induction and Faraday’s Law dΦ=Φ(t + dt) −Φ(t) 0 d d t Φ 0 与回路取向相反 Φ 0 （ B 与回路成右螺旋） N B
Chapter 27 Electromagnetic Induction and Faradays Law dge B ①<0 dee <0E>0 ￡与回路取向相同
Chapter 27 Electromagnetic Induction and Faraday’s Law N B Φ 0 0 d d t Φ t Φ d d = − 0 与回路取向相同