Or does it even have one since it runs in a line as opposed to being coiled? I seem to recall from college that it does, and that it follows the “right hand rule”, that is if you point your right thumb in the direction that the current goes, the field “wraps around” the same way your fingers would.
If that is so (and I didn’t just dream that up) could I run a wire or coil near a powerline and measure a current?
Yes it can be done - I remember reading about a farmer who installed some big pickup coils in a barn and stole power from overhead cables. He was successfully sued over it.
It is important to note that you can’t get something for nothing, in the electromagnetic sense, rather than the legal one - when you connect a load to the pickup coil, you will be modifying the field in such a way as to reduce the power flowing in the overhead cable (in the same sort of way that a bicycle dynamo makes it harder to pedal only when the load(light) is connected).
Sort of. But to efficiently get energy from a magnetic field, you need an effective magentic circuit. This requires a highly mangentically conductive core, such as found in transformers and some inductors. For this to work, the wire has to pass through the interior of the core, else the field will be rejected. In order to capture any useable amount of power, you’ll need to have many, many turns of wire around your core as well. What you’ll have is essentially a current transformer–your output from the secondary will vary in direct proportion to the current through the power line. Power-handling capability of a transformer is largely limited by the size of the core, so to steal an appreciable amount of power, you’ll need a fairly large core. I don’t think this is going to pass unnoticed by the power utility.
Regulating the output voltage of your transformer is going to be tricky as well. The output will vary as a function of the load on the output as well as variations in the current of the power lines In addition if there are two or three lines, usually three in a 3 phase circuit; they tend to be fairly close together and thus would be largely self canceling. This is due to the fact that the current flow is balanced between the lines, as it flows out in one it flows bask in the others. Thus you are collecting more than one field, and they are in opposite directions.
The other way to do it is to use an air core and put a tuning capacitor in the secondary (and preferably in the primary too.) That’s what radio transmitters do: big air-core coils wound out of copper tubing. You’d think that such a thing couldn’t work. As I understand it, the tuned secondary / tuned primary causes the coupling to increase when compared to just an air core transformer…
Or you could install a fluorescent light fixture. Free light!
I don’t think so. What double tuning does is increase the selectivity of the circuit so you need fewer transformers to discriminate against adjacent channels than would be the case with single tuning. By adjusting the coupling between primary and secondary, either by spacing or using a small capacitor, you can make the response of a double-tuned transformer virtually flat in the pass band and with fast (12dB/octave) roll off. Such transformers are impractical at 60 Hz.
In order to get power from the magnetic field from the current in the power line you would need to put a magnetic core around the wire. I don’t think air core transformer would do the job. I’m fairly sure that the utility would notice this pretty quickly.
The power line is also a source of electro-magnetic induction fields which can be picked up with a loop antenna. You might get some power that way. And, of course there is a radiation field but at 60 Hz. there isn’t very much radiation per unit length of power line so you would need a pretty long antenna or a pretty good sized loop antenna.
David Simmons: You’re a guy in your 70’s, yes? You served on the field in Germany in World War II, yes?
Sir, based on the post above, your knowledge of engineering and your excellent writing deserves a profoundly thankful round of applause.