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Cubslover
Can someone explain in simple terms.... Reactance.

Both capacitive and inductive reactance.

I know in capacitive reactance circuits, the current lags the EMF by pi/2 and in inductive reactance circuits, the current leads the EMF by pi/2.

Can someone explain the theory behind this?

I'm trying to learn basic instrumentation for work.
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14 comments

Date Votes
  • Jacob2008
    quote:Originally posted by cubslover
    Can someone explain in simple terms.... Reactance.

    Both capacitive and inductive reactance.

    I know in capacitive reactance circuits, the current lags the EMF by pi/2 and in inductive reactance circuits, the current leads the EMF by pi/2.

    Can someone explain the theory behind this?

    I'm trying to learn basic instrumentation for work.


    Huh...
    Sounds intresting!
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  • Cubslover
    quote:Originally posted by Jacob2008
    quote:Originally posted by cubslover
    Can someone explain in simple terms.... Reactance.

    Both capacitive and inductive reactance.

    I know in capacitive reactance circuits, the current lags the EMF by pi/2 and in inductive reactance circuits, the current leads the EMF by pi/2.

    Can someone explain the theory behind this?

    I'm trying to learn basic instrumentation for work.


    Huh...
    Sounds intresting!


    You have no idea. In one way, all this makes sense, but in another I have no clue.

    Mainly because I'm not being taught, I'm teaching myself.

    Just to show you some of this, instead of typing out of my text, here's a link or three. This is just the beginning...

    http://en.wikipedia.org/wiki/Reactance

    http://en.wikipedia.org/wiki/Inductance

    http://en.wikipedia.org/wiki/Transformer
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  • Jacob2008
    [B)][B)][B)]

    I'll stick with spanish and drafting. ;)
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  • pitbud5
    Sorry I only care to understand automotive electrical circuits
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  • ljwrench
    All I remember is the "eagle flies over the indian and the rabbit"
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  • Cubslover
    quote:Originally posted by ljwrench
    All I remember is the "eagle flies over the indian and the rabbit"


    Ha, I've never heard that way of remembering it. Thanks.

    Come one guys, I really need this help.
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  • Mercury
    Ugh........too long ago for me to remember the details. Get a "Grobe" textbook and read up.

    Merc
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  • SuburbanNoize
    my dad was a union electrician for 20 years, he worked in a steam turbine, combined cycle power plant, when i get home ill ask him, im almost certain he can help you.
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  • bpost
    I took the capacitance reactance courses 17 years ago. I will go find my books and see if I can remember how it worked. If I can't; just sum it up to FM and fuggedaboudit.
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  • Cubslover
    I think it has something to do with the resistance "fighing" the Voltage, that's why the scopes look they way they do.

    With Capacitive Reactance, I believe the resistance is "behind" the voltage as the capacitor fires.

    With Inductive Reactance, the resistance is "infront" of the voltage, causing the voltage to decrease.

    That's why it's a constant "battle". Kind of like a Galvometer/variable resistor circuit.
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  • shoff14
    Remember that voltage is always trying to fight to go go go, it gets held up by things such as coils, capacitors, wires, ect.


    Inductive reactance is the circuit itself creating resistance. In this I mean that they wire, the coils, everything in the circuit resistance, this current wants to go go go through the circuit but is being held up.

    The capacitive reactance in a circuit is the resistance that is created due to a stored charge, for example a capacitor. So this adds another type of go go go in the circuit.

    In order to determine these two things, you need to know the Inductance in the circuit. Inductance is the creating of magnetic fields in the circuit. Things like coils,

    Now with these two pieces of information and the known total resistance of a circuit, you can find the Impedance, which is the total resistance to the alternating current in a circuit. And you are now back to OHM's law.

    So, when you know all the devices in a circuit you can find the total resistance (amps) in a circuit.
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  • Cubslover
    Thanks Shoff....

    So lets get this straight...

    Since capacitors resist the change in voltage, they charge and discharge at a rate to maintaing the same voltage across themselves. Since they fire at the each alternation or reversal of the current, they maintain the same frequency as the voltage. When on a graph the waves of the current lead the voltage wave.

    With Inductive Reactance, the inductors resist the change in current by producing a proportional amount of countercurrent voltage to the voltage coming through it. They also follow the same frequency, but the current waves lag behind the voltage waves.

    Am I getting this?
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  • shoff14
    I will answer a little further tommorow, but your first statement is correct. Second one is a slight miss understanding, its correct in a way though.
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  • Cubslover
    Thanks.

    On the second one, I should have said it produces an equal amount of voltage.
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