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For more information, please see full course syllabus of AP Physics C/Electricity and Magnetism
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Lecture Comments (1)

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Post by Chris Ouyang on May 10, 2015

there's a path of this video where you can't hear anything. 11:10 - 14:15

RL Circuits

  • In an RL circuit, with a battery of emf V, if the switch is closed at time t = 0, then the current in the circuit will be given by I ( t ) = ( V / R )*[ 1 – exp ( -t / T )], where T is the time constant of the RL circuit and is given by L / R. Note that the current rises gradually from 0 to a maximum value of V / R.
  • After the current has reached its maximum value, if we then disconnect the battery at time t = 0, so that we end up with an RL circuit without a battery, then the current decreases in time according to I ( t ) = ( V / R )*exp( - t / T ).
  • Just like a capacitor, when charged, stores electric energy in the space between the plates, an inductor, when it carries a current, stores magnetic energy. The magnetic energy stored in the inductor is ( 1 / 2 ) L I^2.

RL Circuits

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • Current Raising 0:45
    • Battery and Switch with Resistance and Inductance
    • Close s1 at T=0
    • With out Inductor , Current is E/R
    • I at T=0
    • Vb-Va= -Ir
    • Log (i-e/r)
  • Current Declining 27:16
    • Resistance R and Inductance
    • I= E/R
    • Switch is On at T=0
  • Example 39:46
    • Battery and Resistance R Connected with Inductor
    • Time Constant l/R
    • Time to Reach Half Time
    • per τ (1-1/e)
  • Magnetic Energy 45:47
    • E-IR-Ldi/dt
    • Power Derived By Current
    • Magnetic Energy Stored in Conductor
    • U=Li2
  • Magnetic Energy Density 57:49
    • Solenoid
    • U=1/2 Li2
    • Energy Density
  • Example 1: Circuit 1
  • Example 2: Circuit 2