Chapter 30 - Magnetic Induction - FSU Physics Department
Chapter 30 - Magnetic Induction - FSU Physics Department Chapter 30 - Magnetic Induction - FSU Physics Department
Motional emfIt is not necessary for a complete circuit for themotional emf to form. A metal bar movingthrough a magnetic field will have a voltageacross the ends.Inducedvoltage isV = BlvFlux enclosed by the rectangle is φ m = BA = Blx.As the rod of length l moves to the right, the rateof change of flux isd φ dxξ = m = Bl = Blvdt dtThe induced voltage is proportional to the speed atwhich the rod sweeps the magnetic field. Thedirection of current flow is governed by Lenz’slaw.NASA tethered experimentThe wire sweepsthe earth’smagnetic fieldproducing avoltage.PHY2049C - Prof. Ng 4
InductanceA coil that carries a current Iproduces a magnetic field that isproportional to the current. Theflux through the coil is then alsoproportional to I. Theproportionality constant is calledself-inductance, L, i.e.,φ = LISince the induced voltage is equal to the rate ofchange of the flux, the self-induced voltage isd mφξ = −dt= − LdIdtA coil with many turns or a solenoid has a largeself-inductance. The device is called an inductor,L and is represented on circuit diagrams byUnits for L is Henry (H). 1 H = 1 T⋅m 2 /AMagnetic energyRecall that a capacitor stores energy in the electricfield between the capacitor. In a similar, inductorscan store energy in its magnetic fields.The energy stored in an inductor with current I isUm =121 LI2QC2U c=2Compared to energy stored in a capacitorPHY2049C - Prof. Ng 5
- Page 1 and 2: Chapter 30 - Magnetic InductionA ch
- Page 3: Lenz’s lawThe negative sign in Fa
- Page 7: The previous circuit gives the case
Motional emfIt is not necessary for a complete circuit for themotional emf to form. A metal bar movingthrough a magnetic field will have a voltageacross the ends.Inducedvoltage isV = BlvFlux enclosed by the rectangle is φ m = BA = Blx.As the rod of length l moves to the right, the rateof change of flux isd φ dxξ = m = Bl = Blvdt dtThe induced voltage is proportional to the speed atwhich the rod sweeps the magnetic field. Thedirection of current flow is governed by Lenz’slaw.NASA tethered experimentThe wire sweepsthe earth’smagnetic fieldproducing avoltage.PHY2049C - Prof. Ng 4
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