From: ralivingston1952@charter.net   
      
   On Tuesday, February 28, 2017 at 2:02:33 AM UTC-6, John Heath wrote:   
   > I asked this question in an electrical   
   > engineering group. The room went so   
   > quiet you could hear a pin drop. Maybe   
   > physics research group is a more   
   > appropriate place to pose this question.   
   > I will copy and paste the original question.   
   >   
   > This one has been on my bucket list for   
   > a while. How to make a Lorentz contraction   
   > voltage measurement ? It is my hope by   
   > putting some of my failed attempts on the   
   > table that others on the list could breath   
   > new life into this problem.  An out of the   
   > box approach from different shoes that   
   > would not occur to myself.   
   >   
   > First of all what is a Lorentz contraction   
   > voltage measurement. If one probe is grounded   
   > and the other toughing a magnet the voltage   
   > should be extremely negative , 100 KV or   
   > so. Not just a magnet but a copper wire   
   > carrying 10 amps should also have effective   
   > electron contraction leading to an extreme   
   > negative voltage around the wire. However it   
   > can not be measured with a conventional meter   
   > as the meter leads are entering the magnetic   
   > frame of reference therefore it cancels out.   
   > Its a no win.   
   >   
   > Failed attempts on my part. Use a magnetic   
   > probe. Close but no cigar as a magnetic probe   
   >  , current probe , makes a distinction between   
   > north and south poles. Lorentz electron length   
   > contraction makes no such distinction as both   
   > north and south poles have effective length   
   > contraction therefore negative charge. Same   
   > is true of current in a wire regardless of   
   > current direction.   
   >   
   > Build a mechanical mono pole south in and   
   > another north in with flat magnets then   
   > measure the voltage between both opposite   
   > mono poles from the inside. Can not remember   
   > why I thought that would work. Suffice to   
   > say it did not work.   
   >   
   > Not tried yet. A gold leaf jar. Replace the   
   > gold leaf with two pieces of iron then connect   
   > the new iron leaf jar with thin bars of iron   
   > to make contact with the magnet. An iron leaf   
   > jar would not make a distinction between north   
   > or south poles of a magnet as in both cases the   
   > iron leafs would separate a little. However   
   > would this be measuring a Coulomb force caused   
   > by Lorentz electron contraction or just a dirty   
   > trick to lose the distinction between a north   
   > and south poles?   
   >   
   > One more. Sky charge. Sky charge is about   
   > 100 volts per meter or 200 volts from head to   
   > toe. Like the Lorentz electron contraction   
   > this is a voltage that can not be measured   
   > with a conventional meter. The solution is a   
   > voltage field meter. It consist of a fan ,   
   > sheet of copper and a hole on top. If there   
   > is a fluctuating voltage at the copper plate   
   > that equals the frequency of the fan blades   
   > than there is an electric field. Maybe this   
   > would work?   
   >   
   > Any thoughts on this would be welcome.   
      
   I think this is a little bit confused.  The "Lorentz Contraction   
   Voltage" you are talking about is more conventionally called the   
   magnetic field.  I don't know how you calculated 100KV for a static   
   wire, but I think that is based on a misunderstanding of the conditions   
   in a conducting wire:   
      
   Perhaps your calculation would be correct if you took a line charge of   
   stationary electrons with the density in a typical metal and then   
   started that line charge moving.  however in a typical wire conducting a   
   current, unless the wire is itself at a very high voltage there is   
   negligible electric field around the wire.  This is because the way we   
   normally induce a current in a wire, by connecting it to an   
   electromotive force (i.e. a battery or power supply) we force the   
   voltage on the wire to some value wrt our surroundings.  This results in   
   the charge density of the moving charges remaining constant IN OUR   
   FRAME.  The source of the magnetic field when you are moving parallel to   
   the wire is that this balance of charge density does not hold in all   
   frames due to the Lorentz contraction.  Thus a charge moving parallel to   
   the wire does not see balanced positive and negative charges, but an   
   imbalance, either positive or negative, and the acceleration on the   
   moving charge due to this imbalance is the 'magnetic field'.;   
      
   You should note that this Lorentz contraction explanation of the   
   magnetic field only works for motion parallel to the wire.  Magnetic   
   forces on a charge moving perpendicular to the wire are more difficult   
   to explain.   
      
   Rich L   
      
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