Hi,

Moving charges in a conductor do not exert momentum to the conductor carrying them because when the steady state is reached, the movement of the charge (electron) becomes uniform due to the frictional force exerted by the lattice defects on the moving charge. This movement is similar to that of a ball moving in a viscous fluid (or a parachute ballasted in air). 

On the other hand, a macroscopic negatively charged particle moving  from the negatively charged plate to the positively charged plate has a rectilinear movement with uniform acceleration. So, it exerts a momentum on the plates.

For more details, you may open a physics textbook ?

If there was no force electric motors could not work..  One can call them fields but in reality they are forces just like a hand pushing something.

Obviously, for circulating an electric current through an ohmic conductor, it is necessary to maintain a potential difference across the conductor using a device called a voltage generator. Inside a generator, there is coexistence of two opposing fields: the electromotive field Em and the electrostatic field Es. This electromotive field is a characteristic of the generator; it is due to any causes, but is not electrostatic in nature. We then speak of electromotive force of the generator.

Hello,

The metal lattice transfers momentum to the charge carriers (electrons in this case) and vice versa as was shown in the famous 1915-1917 experiments by Tolman and Stewart. They showed that if you accelerate a conductor up to some velocity and then abruptly decelerate it back to zero velocity, the inertia of the charge carriers keeps them moving so that you can measure a pulse of current in an external circuit.  In other words, the essentially free electrons, in the highest level of the metal conduction band, have momentum transferred to them from the metal lattice during the acceleration phase, and then lose this momentum during the deceleration phase as they move through both the stopped conductor and the external, fixed circuit.  Note, the acceleration phase was much slower than the deceleration phase, so the signal was only visible during the quick deceleration.

Tolman and Stewart also verified this effect on aqueous solutions containing fully dissociated salts.  Here the charge carriers would be ions.  In this case, the conducting solution was sealed in an elongated glass vessel with electrodes at either end.  The electrode were connected by insulated, flexible wires to a fixed galvanometer.  The glass tube, oriented so that its long axis was vertical, was then dropped into a box filled with sand.  Again, the signal was visible during the abrupt deceleration.

R. C. Tolman, T. D. Stewart; The electromotive force produced by the acceleration of metals; Physical Review; Vol. 8 (2nd Series); No. 2; August 1916; pp. 97-116.

R. C. Tolman, T. D. Stewart; Mass of electric carrier in copper, silver and aluminum; Physical Review; Vol. 9;  Feb. 1917; p. 164-167.

Also see, Edward M. Purcell; Electricity and Magnetism, Berkeley Physics - Volume 2; Education Development Center, Inc.; 1965; p. 423, Problem 4.26.

Regards,

Tom Cuff

Hello,

Thank you very much. It's really very interesting.

Hello,

Mohamed: You are welcome.  Tolman's papers are interesting to read.

George: You are right about inductance being the electrical manifestation of charge carrier mass and its concomitant inertia.

Max: Two other citations to Tolman's work:

R. C. Tolman, S. Karrer, E. W. Guernsey; Futher experiments on the mass of the elctric carrier in metals; Physical Review; Vol. 21; No. 5; May 1923; pp. 525-539.

R. C. Tolman, L. M. Mott-Smith; A further study of the inertia of the electric carrier in copper; Physical Review; Vol. 28; Oct. 1928; pp. 794-832.

With respect to your original question, here is the unequivocal answer by Barnett,

"If a current in a cicircular coil of wire free to move about its axis is started or stopped or altered, the free electricity will be accelerated, and the coil itself will be accelerated in the opposite direction."

S. J. Barnett; Models to illustrate gyromagnetic and electron-inertia effects; The American Physics Teacher [from 1940 onward: American Journal of Physics]; Vol. 5; No. 1; Feb. 1937; p. 1-6 [Above quotation on p. 6, 2nd column.].

The original experiment demonstrating angular momentum transfer between electrons and the metal lattice is found in,

S. J. Barnett; A new electron-inertia effect and the determination of m/e for the free electrons in copper; Philosophical Magazine; Vol. 42; 1931; pp.349-360.

I apologize for not mentioning this earlier, but I had to check my paper files, first.  My memory is very poor.

Tillmann: Thanks for your support.

Regards,

Tom Cuff

Hello,

Talk about my memory being poor, I just realized something.  You can demonstrate momentum transfer between the conduction electrons and the metal lattice without resorting to the elegant experiments of Tolman and Barnett, or invoking the concept of inductance and its implications with respect to free electron mass and inertia.  The well known phenomenon of electromigration, which manifests itself in the tiny traces used to connect components in micro-electronic circuits, is due to momentum transfer.  In other words, if you have a thin, narrow, aluminum trace, for example, carrying a steady direct current, the electron "wind" created by the relentless flow of conduction electrons can and does move enough material (lattice cores) to create voids in the trace.  It is a well-known failure mechanism in micro-electronics.

Regards,

Tom Cuff

Dear Max,

not only "negatively charged particle" can exert momentum but also electromagnetic radiations or photons, if you prefer, can do. See the link attached.

http://spectrum.ieee.org/aerospace/astrophysics/finding-the-source-of-the-pioneer-anomaly

Hello,

Mohamed: I agree with what you said in your first two posts.  If there is no EMF (battery, generator, external acceleration, etc.) the charge carriers exhibit Brownian motion, and so there is no net force on the lattice.  If, however, an EMF is imposed, then there is a unidirectional flow of charge carriers due to their non-zero drift velocity and an equal and opposite mechanical reaction from the lattice.  Do I have that right?

Max: I am still confused about exactly what your research is.  Can you tell us in more detail?  Initially, I thought the negative charge was moving from the negative capacitor plate to the positive plate through the external circuit, but Mohamed's first post indicated that this charge was moving through the space between the capacitor plates.  I'm guessing that Mohamed's interpretation is the correct one, since you mentioned that the negatively charged particle was macroscopic in size.  How big is macroscopic?

Simone: If I remember correctly, the tails of comets are pointed away from the Sun due to photon pressure, or has that explanation been revised?

Regards,

Tom Cuff

Hello,

I was a little bit afraid because what I said is what I taught to my students for many years. Thank you Tom for your support. Further, I absolutely agree with you about the other aspects of the topic. Your rich memory has summarized perfectly these interesting phenomena.

Of course, we need more details about Max research.

Moving charges like electron can exert momentum to diffused metal ions, like in heavily doped semiconductors in case of very high current density. Electromigration

Just to answer your requests. I am working on how to apply a pd across a satellite to give it an electric charge to enable orbital adjustments against the Earth's magnetic field. Any ideas are welcome.