From: PointedEars@web.de   
      
   Kuan Peng wrote:   
   > Le 29/01/2026 à 04:19, Thomas 'PointedEars' Lahn a écrit :   
   >>> Le 27/01/2026 à 22:37, Thomas 'PointedEars' Lahn a écrit :   
   >>>> I wonder how there is a current in (the secondary) coil B at all *before*   
   >>>> electromagnetic induction.  Usually there is not, i.e. the secondary coil   
   >>>> is NOT connected to a voltage source, but to some electric appliance:>   
   >>   
   >>> 1.	Before the current circulates in coil A, there is not a current in coil   
   >>> B .   
   >>> 2.	After the current circulates in coil A, a current is induced in coil B.   
   >>   
   >> In practice there is no "circulating current" as it is an "alternating"   
   >> current to maximize the induced current.   
   > By " Before the current circulates in coil A "  , I mean " Before the   
   > current occurs in coil A "   
   >   
   > You think the current to be "alternating",   
      
   It is alternating.   
      
   > I think it to be direct,   
      
   Merely an academic possibility.  In real life, a transformer transforms high   
   voltage to low voltage or vice-versa because the current is an alternating   
   current.   
      
   >> Also, in general you should not think of electricity as electrons (or worse,   
   >> positive charges) flowing through a conductor from one end of a circuit to   
   >> the other, like flowing water.  That is NOT how it works:   
   > Is electron beam an electric current?   
      
   Yes.   
      
   > Do we use Maxwell’s equations to describe its behavior?   
      
   Yes.   
      
   Your point being?   
   >> Veritasium: The Big Misconception About Electricity   
   >> https://youtu.be/bHIhgxav9LY   
   > I have viewed this video a while ago. I think he is not a specialist of   
   > electromagnetism.   
      
   You are not in a position to make an informed judgement because evidently   
   you have never studied physics.  He has, and so have I; he is correct.   
      
   > Here too, we see the same video but have different interpretation.   
      
   I am not interpreting, I *know* because I have studied it.  *You* are   
   interpreting because you do NOT know.  Big difference.   
      
   >>> 4.	Because the current in coil A increases linearly, the magnetic field in   
   >>> coil B increases linearly   
   >>   
   >> This could only be said of the _average strength_ of the magnetic field (but   
   >> it would be wrong regardless, see below).  The magnetic *field* is a   
   >> *vector* *field*; it does not make sense to say that a field increases,   
   >> especially not a vector field.   
   > The flux of magnetic field is a scalar and can increase.   
      
   Yes.   
      
   > The induced voltage   
      
   Voltages are not induced.   
      
   > is proportional to the rate of increase of the flux.   
      
   Only because of the electric field that is induced by the change of the   
   magnetic (flux density) field.  We have been over this already.   
      
   >>> and its rate of change is -∂B'/∂t which is constant.   
   >>   
   >> No.  You have to consider that any change of the magnetic field also induces   
   >> a current that flows opposite the current that produced the non-zero field   
   >> values -- Lenz's Law -- which I had indicated by putting primes in the   
   >> *second* induction equation.   
   > The rate of change of the flux is constant, then the induced voltage is   
   > constant.   
      
   Read again what I wrote.  *facepalm*   
      
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   PointedEars   
      
   Twitter: @PointedEars2   
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