Re: Electric Fences

Boo <reply_to_group_not_me@xxxxxxxxxxxxxxxxxxx> wrote:
Gordon wrote:

Actually a current in a straight piece of wire does generate a
magnetic field. In a coil the field is bigger because all the fields
surrounding each part of the wire add up. That's why you should
"flake" rather than coil any spare extension wire when you're mowing
the lawn, that way the fields subtract rather than add.

More importantly, it prevents heating of the coil!
I always run out the full length of extension leads from their housings,
remembering when my teenage kids used one for a 2kw heater and melted
the whole cable and casing. 8-(

Yes, I wasn't trying to say it was avoiding magnetic fields that is the reason
for flaking the lead it's the inductive heating effect. Rogers' point about the
live and neutral fields cancelling is a good one and I can't now remember the
actual mechanism behind it ?

No no no no no! It's purely a resistive heating effect - the current in
the wire multiplied by the square of the resistance. If it's all coiled
up there's no way for the heat to dissipate. If you uncoil it it
dissipates normally and the wire stays relatively cool.

--
Nobby Anderson
.

Relevant Pages

  • Re: Blowing Fuse (12 Volt) in MH
    ... you don't have any laying around and rip out the coil. ... just made a magnetic field detector. ... Disconnect the circuit in question. ... energized wire you'll hear a hum. ...
    (rec.outdoors.rv-travel)
  • Re: OT Question for Iggy
    ... superconducting magnet with a homogenous cylindrical volume of about 2" ... It's the magnet for a Fourier transform ... For whatever reason Oxford favored small diameter wire and lots of turns, ... which has the effect of making the inductance of the coil very large. ...
    (rec.crafts.metalworking)
  • Re: DiMarzio humbucker in an Ibanez guitar (5 way switch)
    ... and then take the bare and solder it onto a separate ground lug. ... Next - take the red wire and wire it the same as the hot wire on the ... your coil tap) to where the white lead was on the Ibanez. ... some pickups DiMarzio makes have good designs for getting both humbucker and ...
    (alt.guitar)
  • Re: coil gauge
    ... there are the same weight of magnet wire to do the coil. ... I am not finding much information on this (different gauge size Vs ... The strength of the magnetic field will be determined by the number ...
    (sci.electronics.basics)
  • Re: Mercruiser Still Wont Start
    ... 12V to the coil thru contacts in the slave solenoid. ... If you can crank it then you do have power to the system. ... beginning point to see if you have 12v being supplied to the wire lead. ...
    (rec.boats)
Loading