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Published byJesus Hammond Modified over 2 years ago

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AC & Inductors In DC circuits an inductor limits current momentarily when: the circuit is first turned on and the current is increasing from zero to full power. the circuit is shut down and the current is dropping from full power to zero. How will the inductor behave in an AC circuit?

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As V source is increasing, V L will be induced in the opposing direction -> acting very much like a resistor! So, V L = I X L where X L is the REACTANCE of the inductor In an AC circuit the current is always changing so the inductor will always be creating a magnetic field that induces a voltage that opposes the sourcec voltage of the circuit. Inductors in AC circuits What factors will affect this Reactance?

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Inductance (amount of flux induced per amp) The larger the inductance, the larger the opposing voltage will be, thus the larger the ability to limit current. So X L L Frequency The larger the frequency the faster the change in current, thus the larger the opposing voltage and the ability to limit current. So X L ƒ Factors Affecting the Reactance of an Inductor: X L = 2 ƒL What will the phase Relationship look like for V L, V R. V S ?

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Phase Relationship for Voltages in a R-L Circuit VLVL VRVR VLVL VRVR VSVS V L leads V S by º V R lags V S by (90- )º V S 2 = V L 2 + V R 2

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Impedance And what does this mean for Impedance? VLVL VRVR VSVS V S 2 = V L 2 + V R 2 V L = IX L V R = IR V S = IZ XLXL Z R Z 2 = X L 2 + R 2

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Summary: Reactance: Voltage: Phase Difference: Impedance: V S 2 = V L 2 + V R 2 X L = 2 ƒL Z 2 = X L 2 + R 2 V L leads V S V R lags V S

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