Week 11 Day 2 Inductors in circuits Circuit element with self inductance Ideally it has zero resistance Concept Question Inserting a Core Correct answer 1 If you insert an iron core into a current carrying coil in an LR circuit the time constant increases Ideal Inductor Electromotive Force Negative sign indicates back emf produced by inductor Emf generated by an inductor is not a voltage drop across the inductor Electromotive force due to electrical forces produced by chemical reactions near terminal For an ideal battery V Moving across an inductor in the direction of current contributes Moving across an inductor opposite the direction of current contributes Ideal Battery emf Faraday s Law for RL Circuit Kirchhoff s Modi ed Loop Lap V 0 Sign Conventions Inductor RC Circuit Increasing Current RC Circuit Decreasing Current Math review Exponential Decay Mass on a spring Energy Analog RLC Circuit When switch S is opened and S is closed at t 0 Consider function A where A t 1 A A decays exponentially A t A Inductors are like masses have inertia Capacitors are like springs store and release energy Batteries supply external force EMF Change on capacitor is like position Current is like velocity Analog LC Circuit Mass doesn t like to change velocity Kinetic energy associated with motion Inductor doesn t like to have current change Energy associated with current Springs do not like to be compressed or extended Potential energy associated with compression Capacitor doesn t like to be charged Energy associated with stored charge x t v t K U
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