821.1 Faraday's law of electromagnetic induction 3. Faraday's law of electromagnetic induction faraday discovered that the induced emf around a closed path is equal to the negative of the time rate of change of the magnetic flux through the same path d induced emf dt Change by magnetic field 更=B.dA Change by area of loop s 21.1 Faraday's law of electromagnetic induction dgp emf=-N“m= d(nm) dy dt dt emf em Reference direction n>0, >0,<0 >0,Q空 <0,E>04 3. Faraday’s law of electromagnetic induction Faraday discovered that the induced emf around a closed path is equal to the negative of the time rate of change of the magnetic flux through the same path t Φm d d induced emf = − §21.1 Faraday’s law of electromagnetic induction ∫ Φm = B⋅ A r r d Change by magnetic field Change by area of loop 0, 0 d d > 0, > ε < t Φ Φ m m 0, 0 d d > 0, < ε > t Φ Φ m m t Ψ t NΦ t Φ N m m m d d d d( ) d d emf = − = − = − §21.1 Faraday’s law of electromagnetic induction emf emf + + Reference direction