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Unit 14: Inductors in DC Circuits

For most of this course you've studied circuits with resistors and DC voltage sources. In Unit 13 we added a new component, the capacitor. This unit will add another new component, the inductor. As you'll see, the techniques and equations for analyzing circuits with inductors are very similar to the techniques and equations that you've learned for capacitors.

Recall that resistors oppose the flow of current. And capacitors store charge. What about inductors? They oppose changes in current. What does that mean? Suppose that a circuit with an inductor has a certain current flowing through it. If you try to increase or decrease that current, then the inductor will fight against you, and will try to keep the current at its initial value. Eventually the inductor will lose this fight, and the current will change, but this will take some time to happen. This is different from what happens in a circuit with no inductor: if there's no inductor, then the amount of current can increase or decrease immediately. If there is an inductor, changes in current take a while to happen.

Unit 13 Review

Preview of Electromagnetism
Inductance of a Coil
Winding Resistance
Inductor Types
Chokes and Coils

Energy Stored in an Inductor

Inductors in Series
Inductors in Parallel
Shortcut Rules for Inductors in Parallel
Series-Parallel Inductors

Series RL Network
DC RL Circuit
Behavior of Inductors in DC Circuits
Initial, Transient, Steady-State
Initial Currents and Voltages
Steady-State Currents & Voltages
Transient Currents & Voltages
Transients: Closing Switch
Calculating i
Time Constant
How Long to Reach Steady State?
Calculating vR and vL

More Exponential Curves
De-Energizing an Inductor

Series-Parallel Transients

Unit 14 Review

Congratulations! You've completed the e-Lesson for this unit. This concludes your study of DC circuits. Congratulations on making it through to the end! For a good review, I suggest that you go back and re-take each of the Unit Review self-tests (located at the end of the e-Lessons).

Of course, there's plenty more to learn. In this course we've concentrated on analyzing circuits that contain DC voltage sources and DC current sources. In later courses, you'll learn about circuits with AC sources instead of (or in addition to) DC sources. To get a head start on these topics, take a look at the material that you'll study in EET 1155.