PHY132_L21 - Classical Physics II Classical Physics II...

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lassical Physics II Classical Physics II PHY132 Lecture 21 AC Circuits Lecture 21 1 03/19/2010
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Self Inductance Whereas Mutual Inductance describes the effect of a changingcurrent in one coil on another coil, there is also an induced EMF in the first coil ITSELF! – That is (or should be) completely expected: • a coil carrying a changing current , itself experiences the changing flux as ell and thus should itself experience self- duced MF well, and thus should itself experience a self induced EMF… –the self-induced EMFimplies the existence of a voltage difference Δ V between the terminals of the coil … hat pposes the original current hange • that opposes the original current change Taking the definition of mutual inductance, we can easily define the SELF-INDUCTANCE L : here the elf- duced EMF ue to the changing 1 1c o i l di V dt   E L (Note the "symbolic" sign!) Lecture 21 2 where E 1 is the self induced EMF due to the changing current i 1 03/19/2010
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Series E LR Circuit Initially, switch S is open; at time t= 0 the switch is closed Kirchhoff’s Rule #2 in this circuit: S i ( t ) 0 di Li R dt  E R L E t d t 0 di Vi R L dt  0 1 Ld i R d t  () it Ldi L di 0 VRi t x t L 0 td 00 ) t LR VV t e  0 0 R 0 0 / R VR i 0 VR R x   0 0 ln R  0 1 t V e ) t di t Ve  Equivalently: the Voltage across the resistor: ( ) R V it R t R R   R i 0 L L d Vt t 0 1 t
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This note was uploaded on 04/14/2010 for the course PHY 132 taught by Professor Rijssenbeek during the Spring '04 term at SUNY Stony Brook.

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PHY132_L21 - Classical Physics II Classical Physics II...

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