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What does the j stand for in an impedance calculation?

wikiHow Staff Editor
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wikiHow Staff Editor

Staff Answer

The j stands in for the imaginary number √(-1). Normally you would use i for this, but j is used in impedance calculations to avoid confusion with I for current.

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Question

How do I calculate line impedance?

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This answer was written by one of our trained team of researchers who validated it for accuracy and comprehensiveness.

wikiHow Staff Editor

Staff Answer

Line impedance is the ratio of complex line voltage to complex line current. You can calculate it with the following equation: Z(z) = V(z)/I(z).

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Question

How do I calculate the impedance of the coil connected in series with the capacitor?

Community Answer

If the coil has a resistance, then treat it as an LCR circuit. Z = [(Xc-XL)^2 + R]^0.5, where Z is the impedence, Xc is reactance of the capacitor which is equal to 1/(wC), w being the angular frequency and C being capacitance. XL is reactance of the coil which is equal to wL, L being the inductance of the coil, and R is resistance of the coil. Put R = 0 in case the coil has no resistance.

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Question

How do I find the resistance needed for a circuit with 6 volts to get a power drain of less than one amp?

Community Answer

You mention that you want amp, but describe it as power. They are not the same. Power is watts and amperage is amps. Assuming you mean amperage: I = E/R. That is, amps = voltage divided by resistance. If you want 1 amp @ 6 v, then you need a 6 ohm resister (1 = 6/6). If you want less than one amp, then you would need more than 6 ohms of resistance, given the same voltage.

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Question

How do I calculate impedance when resistance is not given?

Community Answer

When there is no resistance, it means R = 0.

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Question

How do I determine generator voltage?

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You have to get an electronic tester. It will tell you exactly how many volts of power something is drawing.

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Question

How do I calculate impedance when I know the resistance, inductance, and voltage of a circuit?

Jim Coombes

Community Answer

This is shown in part 2 step 4: Z = square root ( R^2 + X^2), just use the inductive reactance value since there is no capacitive reactance.

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Question

Why can't impedances in a series be added to find the total circuit impedance?

Jim Coombes

Community Answer

The reason behind this is how capacitors and inductors react to changing currents or voltages in an AC circuit. This is mentioned in part 1 step 3 just a little bit. Capacitors oppose changes in voltage so the current and voltage are 90 degrees out of phase with current leading the voltage. Inductors oppose changes in current so it is out of phase with the voltage and the voltage leads the current by 90 degrees. If you are interested in knowing more, please let me know and I will try to put together an article on this topic: Calculating AC phase angles.

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Question

How do I solve for impedance with a capacitor and inductor in a parallel with another capacitor and resistor?

Jim Coombes

Community Answer

I can't give you a complete answer until I know the circuit set up. Is the first capacitor and inductor in series with each other or in parallel? Is the second capacitor in series with the resistor or in parallel? Basically, are there two different circuits in parallel with each circuit having 2 series components?

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