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Inductor

Inductor. Inductor. An inductor is a device that temporarily resists change in current flow. http://www.falstad.com/circuit/e-induct.html (Please try this applet). Inductor at t=0. Inductor resists the currently initially .

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Inductor

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  1. Inductor

  2. Inductor • An inductor is a device that temporarily resists change in current flow. • http://www.falstad.com/circuit/e-induct.html (Please try this applet)

  3. Inductor at t=0 Inductor resists the currently initially. VL jumps to 2.5 V because there is no current in the resistor initially.

  4. Inductor at t>0 Inductor slowly gives up its resistance to current Current begins to increase Voltage across the resistor begins to increase while the voltage across inductor begins to drop. (Can you explain why?) 4. What is limit of the current in the circuit?

  5. VS transitions to 0V What happens when VS switches from 2.5 V to 0V? L resists change in current. So initially the resistor will carry 0.25 mA of current. Since VS is 0V, VL will be -2.5V.

  6. The Inductor stops resistant the change in current. The current will slowly decrease to 0.

  7. Plot Inductor Current as a function of time The current in an inductor can not change instantaneously.

  8. Exponential Current Buildup

  9. Current versus time More details in Chapter 7

  10. Exponential decrease of current

  11. Current versus time

  12. Why Does an Inductor Oppose Change in Current?

  13. Magnetic Field (Magnetic field) Current Note: The field is stronger closer to the conductor and becomes weaker with increasing distance from the conductor.

  14. Right-Hand Rule Thumb: Points in the direction of current Fingers: point in the direction of the magnetic lines of force. Reference: (Floyd, p. 384)

  15. Different Ways of Building Inductors on Silicon

  16. Inductance Calculator http://www-smirc.stanford.edu/spiralCalc.html

  17. Cumulative magnetic force

  18. Application: Electromagnet When the coil of wire is connected to a battery, there is current. A magnetic field is established.

  19. Faraday’s observation • A changing magnetic field can induce a voltage in a conductor.

  20. Faraday’s First Observation The amount of voltage induced in a coil is directly proportional to the rate of change of the magnetic field with respect to the coil.

  21. Faraday’s second observation The amount of voltage induced in a coil is directly proportional to the number of turns of wire in a coil. The induced current generates a voltage across the input resistance of the voltmeter.

  22. Lenz’ law When an emf is generated by a change in magnetic flux according to Faraday's Law, the polarity of the induced emf is such that it produces a current whose magnetic field opposes the change which produces it. http://hyperphysics.phy-astr.gsu.edu/HBASE/electric/farlaw.html#c2

  23. Mathematical Definition

  24. Inductors Connected in Series

  25. Inductors Connected in Parallel

  26. Derivations • Details shown in class

  27. Use an Impedance Analyzer to Measure Inductance

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