Re: SR and electrical resistance, and rates

From: Bill Hobba (bhobba_at_rubbish.net.au)
Date: 02/14/05 

Date: Mon, 14 Feb 2005 06:07:57 GMT

<dseppala@austin.rr.com> wrote in message
news:42101185.434305646@news-server.austin.rr.com...
> On Sun, 13 Feb 2005 05:46:28 GMT, "Bill Hobba" <bhobba@rubbish.net.au>
> wrote:
>
> >
> ><dseppala@austin.rr.com> wrote in message
> >news:420eaef7.343525275@news-server.austin.rr.com...
> >> On Sat, 12 Feb 2005 22:36:56 GMT, "Bill Hobba" <bhobba@rubbish.net.au>
> >> wrote:
> >>
> >> >
> >> ><dseppala@austin.rr.com> wrote in message
> >> >news:420e6794.325247952@news-server.austin.rr.com...
> >> >> It is easy to setup an electrical circuit where one segment of wire
is
> >> >> moving relative to the other wires and components in the circuit.
> >> >> Does any know how the resistance of a moving wire changes as a
> >> >> function of relative velocity per Einstein's theory?
> >> >>
> >> >> Does the orientation of a resistor wrt two different inertial
> >> >> reference frames affect the resistance? If so how?
> >> >>
> >> >> Also, the DC generator on my bicycle outputs a voltage proportional
to
> >> >> how fast the generator shaft is spinning. If a moving frame
measures
> >> >> the spin rate of that generator shaft to be half of the spin rate of
> >> >> an identical generator that is in the moving frame, how do the
moving
> >> >> frame observers explain the output voltage measurements of the
> >> >> generators?
> >> >
> >> >Without working out the details it is obvious the magnetic field the
> >> >generator 'cuts' to produce the voltage and the voltage itself changes
> >from
> >> >frame to frame as per Maxwell's equations. The spin rate obviously
will
> >be
> >> >seen as consistent with these new values. However rotating frames in
SR
> >are
> >> >notoriously difficult to analyze due to problems with simultaneity.
> >> >
> >> >Bill
> >> If we have a straight wire, how does its resistance change as a
> >> function of V?
> >
> >It doesn't. Resitance is invarient.
> >
> >> Its easy to build a circuit in which one straight wire
> >> is moving relative to another wire, and have an electric current flow
> >> through both wires in a series, or parallel connection. But its not
> >> clear to me how things work with Einstein's length contraction.
> >
> >You must be more precise about your experimental setup for a comment.
> >
> >>
> >> No one posted an answer to my posting about SR, time dilation, and
> >> electric circuits. The circuit I posted there was symmetrical, so
> >> volt meters, clocks, amp meters, etc. at the opposite two ends of the
> >> two wire circuit have to read the same values in at least one frame
> >> but not necessarily the same in other inertial frames. But in other
> >> frames if the values aren't the same (per Einstein's notion of
> >> simultaneous events in one frame being non-simultaneous in other
> >> frames), then more charge (electrons per second times seconds) enter
> >> one side of the circuit then leave the other side, yet the wires don't
> >> become charged.
> >
> >Please post the precise details of your setup. I did not see your
previous
> >post. And when I say precise - I mean precise. If it is not then I will
> >ask you to elaborate. It is well known that SR is as consistent as
> >Euclidian geometry so you have not discovered problems - all you are
really
> >doing is confusing yourself by coming up with more and more difficult
> >situations to analyze. That is the reason I want a precise description -
it
> >is no use analyzing complex setups with the added difficulty of them
being
> >vague.
> >
> >Thanks
> >Bill
> Here's the details of my previous post. It was posted under the
> thread named SR and electrical circuits ...
>
> Given identical wires, wire A and wire B. Both wires are parallel to
> the x-axis. Wire A is at y = 1, and wire B is at y = -1. Across
> wires A and B I have a battery, and an electron counter and a clock at
> the same location. I will call these items battery A, clock A and
> electron counter A. Battery A and electron counter A are wired in
> series connecting wire A to wire B. Battery A and electron counter A
> and clock A are all physically tied together so that they are always
> at the same relative x-coordinate. One terminal of the battery is
> soldered (physically attached) to wire A. The other end is physically
> attached to the electron counter, and the other end of the electron
> counter touches wire B, but is not physically attached. It just
> touches the wire with brushes, or a metal wheel to make electrical
> contact.

I have read so far and do not see the relation of the setup to resistance.
Remember what resistance is - R = V/I where resistors are devices such that
R is for all intents and purposes intendment of the V and I. Such has
notihng to do with electron counters and wires.

> I also have another identical set of items, battery B, electron
> counter B, and clock B. Battery B, electron counter B and clock B are
> all physically tied together so that they are always at the same
> relative x-coordinate. Battery B and electron counter B are wired in
> series, but in the opposite direction of battery A and electron
> counter A. One terminal of battery B is soldered (physically
> attached) to wire B. The other end is physically attached to electron
> counter B. The other terminal of the electron counter touches wire A
> but is not physically attached to it. It just makes electrical
> contact to wire A through brushes or a metal wheel. Now when both
> sets of these batteries and electron counters are attached, current
> flows through the circuit and each electron counter counts the same
> number of electrons passing through the circuit each second.
> Now lets say these elements are at x=0 at time t0, when we make the
> connections. Let wire A, battery A, electron counter A, and clock A
> be called inertial frame A. Let wire B, battery B, electron counter
> B, and clock B be called inertial frame B. At time t0, when they are
> all located at x=0, let Frame A have a relative velocity wrt to frame
> B equal to V. At that same time and point in space, we make the
> connections so that a current flows in this circuit, set both clock A
> and clock B to read zero seconds, and we initialize the electron
> counters to zero.
> The two clocks, the two electron counters and the two batterys are
> now moving away from each other with relative velocity V. Current is
> flowing in the circuit. The current flows from battery A through
> electron counter A, then through wire B, through battery B, and
> electron counter B, and then back through wire A to battery A. We
> all know we can build such a circuit for small values of V, so we know
> current will flow through the circuit as described.
> Now at time tN as measured by clock A, electron counter A shows
> that N electrons have passed from wire A to wire B. The question I
> have is at that same time as measured by observers in frame A, what
> does clock B and electron counter B show? Einstein says clock B is
> running slower than clock A as measured by observers in Frame A.
> Therefore, electron counter B must measure that fewer than N electrons
> traveled from wire B to wire A when clock A reads time = tN. If
> more electrons go into wire B than leave wire B, wire B must
> accumulate negative charge, and wire A must become positively charged.

Wait a minute - you must compare electrons going in an out of the wires in
each frame. Current is conserved in each frame but is not necessarily the
same. Again what has this got to do with resistance?

> Let observers in frame A test that consequence. Let a charged
> particle travel between the two wires in the X-Y plane at x=0, half
> way between the wires. Is there any point on that wire where the
> charged particle moves toward wire A and away from wire B? When
> observers in frame B do this same test, they expect this same charged
> particle to move in the opposite direction. I don't see how both can
> be true, and from views in other frames, the charged particle won't be
> accelerated toward either wire. So I don't see how observers in Frame
> A can explain why wire B accumulates negative charge, and wire A
> accumlates positive charge but neither wire affects the motion of a
> charged particle.
> On the other hand, if electron counter B reads N electrons at the
> same time, as measured by Frame A observers, as electron counter A
> reads N electrons, then clock B must also show that tN seconds elapsed
> since both clocks were set to zero when they were both at x=0 at time
> t0. If that is true, observers cannot conclude that clock B is
> running slower than clock A.
> I simply don't see how Einstein's theory works with this simple
> circuit we can build.
> Thanks,
> David Seppala

As far as I can see what you are doing is comparing electron counts in
different frames. Such is not an indication of accumulating charge - that
always must be done in the same frame.

But again I ask - what has that got to do with resistance?

Bill

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