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Unformatted text preview: Inductance Inductance Text sections 32.1  32.3 Practice: Chapter 32, problems 5, 7, 12, 33, 65 a), 65 b) A variable power supply is connected to a coil. The current in the coil creates a magnetic field. What happens when the power supply dial is turned down, reducing the supply current? What happens when the current is turned up? “Self “SelfInductance” Inductance” A circuit carrying current I generates its own magnetic field B ; so there will be a flux Φ B through the circuit. i f I changes, an emf E is induced in the same circuit . (“selfinductance”) Lenz’s Law: E tends to oppose the change in I . (selfinductance gives “inertia” to currents) From the BiotSavart Law, T he selfinductance L is the proportionality constant: unit: 1 henry (H) = 1 volt/(A/s) = 1 (V•s)/A dt dI I I B − ∝ ⇒ ∝ Φ ⇒ ∝ ε B r dt dI L ε − = (definition of L) I N L Φ = dt dI L dt d N − = Φ − = ε (so 1 henry = 1 weberturn/ampere) An equivalent definition of L uses the flux produced per ampere...
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 Spring '09
 Britz
 Magnetic Field, power supply, Energy density, di dt, −L dt dt

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