Blair:
        It has more impedance to current. The word impedance is used instead
of resistance due to the fact that it is an inductor and not a resistor. So
the more impedance the part has the slower the current and more of the
electrical energy turns into heat. A comparison would be a straight pipe
versus a pipe that is coiled where water runs through each one. The voltage
behind the coil would relate to the pressure the water is pumped through the
pipes
        Regards,
        Ramon

> -----Original Message-----
> From: Blair K. Hogg [SMTP:[log in to unmask]]
> Sent: Wednesday, October 08, 2003 8:27 AM
> To:   [log in to unmask]
> Subject:      Re: [TN] Max Current Brain Teaser
> 
> Brian,
> 
> Does the coiled wire get hotter due to the proximity of adjacent coils, 
> the concentration of heat in a small space, or a combination of both? 
> Or do they sound like the same effect expressed differently?
> 
> The straight wire and the coiled wire, if they have the same properties,
> should dissipate the same amount of power in watts, correct? It is the
> proximity and space constraints that cause the temperature to increase.
> 
> Thanks,
> 
> Blair
> 
> 
> >>> [log in to unmask] 10/08/03 02:42AM >>>
> A coiled wire will get much hotter than a straight wire for a given
> current, always. However, I disagree that you should care how hot it
> gets. It can go through phase changes which will reduce the springiness
> if it gets too hot. I don't have phase diagrams for BeCu, so cannot give
> you a max. However, BeCu is precipitation-hardened at about 300°C for
> most usual alloys, so I feel it would be unwise to exceed ~200°C,
> depending on the % of Be.
> 
> Brian
> 
> Jack C. Olson wrote:
> > Does anyone out there enjoy brain teasers?
> > I was asked an interesting question today.
> >
> > We need to have current traveling across a spring.
> > The spring connects a connector pin to a SMT pad.
> > We don't care how hot the spring gets as long as
> > it doesn't melt the board.
> > When the spring is compressed it is only 20 mils
> > away from the board, but the current may have to
> > travel around the circumference, so the distance
> > may be more like 200 mils.
> > The spring material is berrillium copper and the
> > thickness is equivalent to AWG26. So even though
> > a wire of this thickness may be rated 1.7 amps:
> >
> > What is the maximum current we can push
> > through this short distance continously?
> >
> > We have been discussing the fact that even though
> > the wire in your house may be rated for 10 amps
> > and it won't get hot even on a 200 foot run, how
> > much current can you drive through a half-inch
> > piece? Especially if you don't care if it gets hot?
> > Nothing I found on Doug Brook's site (temp calc
> > and fusing current study) seemed to help.
> > ( http://www.ultracad.com )
> >
> > thanks,
> > Jack
> >
> 
> 
> 
> 
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