# Measuring load on a circuit breaker.

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• posted on February 24, 2007, 3:55 am

Doug Miller wrote:

Hi, Filament has an amount of inductance/capacitance. it is very fine coil. Even piece of wire has finite capacitance and inductnace. Why do you think there is a surge current when light bulb is turn on? Ever heard of phase compensating capacitor or lump inductor. Or go inside a power room in any big commercial building, what do you see there? Do you know why electric cable is some times criss crossed or twisted? Simply to answer your question, Yes, really, always. It becomes very critical on high frequency. Todays florescent bulbs are driven by 44KHz current. Pure resistive circuit in real world is problably near none. Z^2 is combination of R and j(Xl-Xc). Remember HS physics class? Xl and Xc cancels each other, equal value, whatever left is either Xl, or Xc. In real world most load is inductive. In inductive circuit voltage is leading and current is lagging. This phase difference produces wasted power which does not do any work. Ideally the phase difference should be zero. That is why KVA is not equal to Watt rating of a device.(efficiency) I spent my working life on RF telecommunication(mobile and fixed base), UPS, MG, Antenna farm, stuff like that.

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• posted on February 24, 2007, 6:48 pm
So many things to respond to. I'll have to reply inline.
--

Christopher A. Young
You can\'t shout down a troll.

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• posted on February 24, 2007, 3:34 pm

Yes.
BTW, it was in dealing with that, that I learned about complex numbers.
None of this changes the logical direction here.
--
Mark Lloyd
http://notstupid.laughingsquid.com

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• posted on February 20, 2007, 10:02 pm

There is usually a black wire connected to the circuit breaker. If you can clamp around that wire with the appropriate ammeter (Google clamp-on ammeter) you can measure the current in that circuit.
What are you trying to accomplish?

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• posted on February 20, 2007, 11:30 pm

I have an adaptor for my ammeter that I can plug into an ordinary wall receptacle. It has a loop on it to clamp around and I can plug an appliance into it to see what the load is for that appliance. I think Amprobe makes it.
John Grabowski http://www.mrelectrician.tv

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• posted on February 21, 2007, 12:30 am
On Tue, 20 Feb 2007 18:30:25 -0500, "John Grabowski"

I'm using a Kill-A-Watt meter for that now, but previously I had a VOM attachment for that. I made it from a remote control cord (just a switch at one end) with the switch removed and replaced with banana plugs.
--
Mark Lloyd
http://notstupid.laughingsquid.com