Class13HO - Class 13 Impedance in AC Crcuits Physics 106...

Info icon This preview shows pages 1–22. Sign up to view the full content.

View Full Document Right Arrow Icon
Class 13 Impedance in AC Crcuits Physics 106 Fall 2011 Press CTRL-L to view as a slide show.
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Learning Outcomes Last time we I learned about generators I looked at the details of a motional emf problem I reviewed for Exam #1
Image of page 2
Learning Outcomes Today we will discuss: I Inductors and self-inductance I RL Circuit Problems I AC Circuit Terminology I R, L, and C in AC Circuits
Image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Inductors and Self-Inductance
Image of page 4
Self-inductance I A coil of wire in a circuit is called an inductor. It produces a magnetic field inside itself. I If the current is changing, it produces an EMF because its own B field is changing in time.
Image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Self-inductance I If current is increasing, the inductor produces an induced current that opposes the current in the circuit.
Image of page 6
Self-inductance I If current is decreasing, the inductor produces an induced current in the direction of the current in the circuit.
Image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Self-inductance I The faster the current changes, the larger the is the induced EMF
Image of page 8
Self-inductance I We define the inductance L of a coil by the relationship: = - L Δ I Δ t I The negative sign indicates that a changing current induces an emf in opposition to that change
Image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Self-inductance I The SI unit of self-inductance is the Henry (H) I A useful expression for L is: L = - N Φ B I
Image of page 10
RL Circuits
Image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Inductors in a Circuit I If an inductor, a resistor, a battery, and a switch are placed in in a series circuit: I Just after the switch is closed, the inductor produces an emf that completely stops the flow of current - but only instantaneously I After a long time, the inductor acts like a wire.
Image of page 12
RL Circuit I As the current gets larger, it changes less, and the inductor’s voltage decreases. I The time constant, τ , for an RL circuit is the time required for the current in the circuit to reach 63.2% of its final value
Image of page 13

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
RL Circuit I The time constant depends on R and L τ = L R I The current at any time can be found by I = R 1 - e - t
Image of page 14
Energy Stored in a Magnetic Field I An inductor stores energy in its magnetic field. U L = 1 2 LI 2
Image of page 15

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
RL Circuit Example I A 3.0 Ω resistor, a 12 mH inductor, and a 12 V battery are connected in series. A switch is closed at t = 0.
Image of page 16
AC Circuit Terminology
Image of page 17

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
AC Circuit I The output of an AC generator is sinusoidal and varies with time according to the following equation I V ( t ) = V max sin 2 π ft I V ( t ) is the instantaneous voltage I V max is the maximum voltage of the generator I f is the frequency at which the voltage changes, in Hz I The period is T = 1 / f
Image of page 18
Average Voltage I V ( t ) = V max sin 2 π ft I The average value of sine is 0 I But that’s not useful
Image of page 19

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Average Voltage I We could try V max | sin 2 π ft | I But absolute values are awkward functions.
Image of page 20
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern