Ohm's Law

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tlaidman

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Impedance

Impedance

You need to know what the type of load is. To find impedence you need to know if the load is inductive, capacitive, or only resistive. you did not give enough information.
 
charlie b

charlie b

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No, there is enough information. Let's say the current is exactly 100 ma. That makes the impedance 1200 ohms (120 divided by 0.100). Now, there is an open question as to how much of that impedance is represented by resistance, and how much by reactance (the R and X values). But you can call the net result "impedance."
 
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gar

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charlie is correct impedance Z = Irms*Erms for a sine wave for current and voltage. Where the sine waves are of any phase relationship to each other.

Not as true a measure for signals with high harmonic content. For example a square wave vs sine wave of the same RMS voltage.

A simple resistor and inductor in series where both resistance and inductance are independent of current or voltage will have a constant value of impedance for different voltages at the same frequency.

If there is harmonic content in the voltage across this series combination the impedance as defined in the above equation will change as you change the harmonic content while holding the voltage constant.

.
 
drbond24

drbond24

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K8MHZ said:
Assuming a current of less than 100mA and making the assumption of a 120 volt AC source, do we have enough information to make a calculated guess at the impedance of the load?

http://www.foxnews.com/story/0,2933,363452,00.html
Click to expand...

I would think it is safe to assume that his wife did not have inductance and that her resistance is far greater than her capacitance, so I'm leaning toward the 1200 ohm answer. :grin:
 
mivey

mivey

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The technician must have known that it would enhance the results if it were possible to overcome the resistance of the outer, dryer layer of the load, thus the need for the addition of the water component. This could reduce the resistance by one or even two orders of magnitude.

It might be noted that the resistance of the load in question is, on average, slightly higher than its companion version as the companion load normally has more of the lower resistivity material that is the main path for current flow.

I would suspect that the load, especially given the high external moisture content, would be almost entirely resistive and the reactance would be two to three orders of magnitude lower than the resistivity, depending on whether the flow was perpendicular or parallel to the fibers of the main current path.
 
C

coulter

Senior Member
r -

rattus said:
... In this case the minimum impedance would be,

|Zmin| = 120V/100mA = 1200 Ohms
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Interesting word choice. Does this imply there are other magnitudes of impedance that are valid? If so, I'm not clear on how that would be.

carl
 
charlie b

charlie b

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coulter said:
Interesting word choice.
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I believe that his use of the word "minimum" was based on wording in the original post, "less than 100 ma." My answer of 1200 ohms was based on a current of exactly 100 ma; if the current is less the resistance must have been higher. So 1200 is a minimum.
 
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rattus

Senior Member
Huh?

Huh?

Was the plumbing not grounded? Even with a metal valve and plastic pipe, the water would have created a path to ground. Sounds fishy to me.
 
LarryFine

LarryFine

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rattus said:
Was the plumbing not grounded? Even with a metal valve and plastic pipe, the water would have created a path to ground. Sounds fishy to me.
Click to expand...
Well, look who's poked his dusty head out of the woodwork! :D

Okay, how conductive would a column of potable water be?
 
mivey

mivey

Senior Member
rattus said:
Maybe 0.05 S/m?
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Which would be near the value for drinking water. The upper range for drinking water is near 0.08 S/m. Potable water is up to 0.1055 S/m.

Pure water is 5.5 uS/m
Distilled water is 50 uS/m
Tap water is 0.05-0.08 S/m
Potable water max is 0.1055 S/m
Sea water is 5.6 S/m
Brackish water is 10 S/m
 
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