Inductors

Discussion in 'Homework Help' started by alexander7, Oct 11, 2009.

  1. alexander7

    Thread Starter New Member

    Oct 11, 2009
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    How much potential energy is stored in a 5 μ H inductor that has a current of 2 ma flowing through it?
     
  2. ELECTRONERD

    Senior Member

    May 26, 2009
    1,146
    16
    Potential energy? I'm not accustomed to that term, I suppose you mean reactance? Then according to the equation:

    XL = 2 \pi f L







    Where:
    • f = Frequency
    • \pi = Pi, or approximately 3.14
    • L = Inductor value.
    So, we can't really determine the reactance unless we know the frequency.
     
    Last edited: Oct 11, 2009
  3. ATM

    Member

    Oct 8, 2009
    31
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    Use the equation, Energy = 0.5*L*I^2

    0.5*(5X10^-6)*((2x10^-3)^2)
     
  4. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    To put ATM's equation into math symbol notation:

    E_{\tiny L} =\frac{LI^2}{2}

    The corresponding equation for capacitors is:


    E_{\tiny C}=\frac{CV^2}{2}


    hgmjr
     
  5. mik3

    Senior Member

    Feb 4, 2008
    4,846
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    E=0.5*L*I^2

    Be careful of the units.
     
  6. notxjack

    New Member

    Sep 7, 2009
    20
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    potential energy is an unfancy word for voltage
     
  7. ELECTRONERD

    Senior Member

    May 26, 2009
    1,146
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    Of course! Now that I think of it, I remember...:rolleyes:
     
  8. Thav

    Member

    Oct 13, 2009
    82
    0

    I don't think this is quite right. Energy is always referring to Joules (J), whereas voltage (or electric potential) is Joules per Coulomb J/C. This has always been a hazy subject for me, but what I think is that if you take an electron (1.6...E-19 Coulombs) and find its potential energy at one point in an electric field with respect to another point and then divide by the charge (that 1.6E-19) you get the voltage. So like the units hint we're talking about a potential energy per charge.

    I'm being a little pedantic, but I feel voltage is such a difficult concept it's important to get the terminology straight to not obscure the physical basis.
     
  9. ELECTRONERD

    Senior Member

    May 26, 2009
    1,146
    16
    In any case, potential energy is still denoted as "voltage", used by many. Even teachers use the termination in universities, and I've heard it a lot in the "self teaching" electronic guides.

    People can think of the relationship between voltage, current, and resistance as the following:

    Imagine a water pipe. More pressure will result in a higher potential of energy coming out; better known as voltage. The higher the pressure, the higher the potential. If we widen the pipe, we get more current. However, if we put a resistor in the pipe, it would lessen the current. That's how I've always found the relationships for ohms law.
     
  10. Ratch

    New Member

    Mar 20, 2007
    1,068
    3
    notxjack,

    Not true. See the first post of the link below.

    Thav,

    Good for you. You are a "right thinker".

    ELECTRONERD,

    Why not "imagine" it the way it really is? As explained in the first post of the link below.

    Ratch

    http://forum.allaboutcircuits.com/showthread.php?t=11579&highlight=treatise+voltage
     
  11. notxjack

    New Member

    Sep 7, 2009
    20
    0
    Yeah, my bad. Integrate work to get the 1/2 mv^2 dual for inductors, which I think is 1/2 LI^2
     
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