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I Comparing inductance and capacitance: Analogy to charge

  1. Feb 21, 2017 #1
    Hi.
    Inductance and capacitance have many analogies, both conceptually and formally. A capacitor connected to a voltage source carries the charge ##Q=C\cdot V##. The analogous equation for inductance is ##n\cdot \Phi=L\cdot I##.

    Charge is physical, it's proportional to the number of excess electrons on one plate. But what exactly is ##n\cdot \Phi##? I know what the magnetic flux is, but I wonder if there's a more tangible interpretation analogous to charge.
     
  2. jcsd
  3. Feb 21, 2017 #2

    Baluncore

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    Science Advisor

    Energy is a fundamental so you might look at the parallel from that viewpoint.

    For a capacitor; E = ½ · C · V²
    Q = C · V
    C = Q / V; the slope of the line dQ/dV = C.
    E = ½ · Q · V; the area under the line is the energy.

    For an inductor E = ½ · L · I²
    Φ = L· I
    L = Φ / I; the slope of the line dΦ/dI = L.
    E = ½ · Φ · I; the area under the line is the energy.
     
  4. Mar 12, 2017 #3

    David Lewis

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    Gold Member

    Current times inductance.
    Inductance tells you how good a conductor is at generating a magnetic field when current flows through it.
     
    Last edited: Mar 12, 2017
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