N. 3 - 21 aprile 2001 - Giano Bifronte

The force (7) is not contained explicitly in the standard Lorentz
expression which turns out to be zero in this case, but it is obtained
from a more general expression that accounts for the internal structure
of the magnetic dipole. Thus, the standard Lorentz expression must be
implemented by (7) in order to account for fm .
A macroscopical experimental test of this force is here considered. In
the AB effect there exists an em momentum Qem = (q/c)Am ≠ 0 , and the
modified Lorentz force
fq = -∂tQem = -(q/c)∂tAm (8)
represents the differential statement of Faraday's law, which has been
tested for closed loops only but not on a single stationary charge. The
test of this force has the same importance of the experimental
verification of basic interaction forces such as those of Newton's and
Coulomb's laws.
The following experiment may be used to test the quantum
interpretation of the AB effect vs. the alternative classical interpretation,
or else, the standard force expression vs. the nonstandard. A long
solenoid or toroid carrying a current i is placed near a macroscopic
charge distribution Q. Both the solenoid and the charge may be kept
stationary and: a) the current may be switched off; or: b) the solenoid
may be removed with velocity v . In both cases an impulse on the
charge,
∫ fdt = -Qem ,
is predicted according to Eq. (8) and can be measured.
In the first case a), the impulse
∫ QEmdt = Qem = QAm
is due to the radiation field Em = -(1/c)∂tAm , and a non-null result of the
experiment represents a test of the Faraday's law in its differential
form. An equal and opposite force acts on the solenoid and solves the
Shockley-James paradox ([7]). Notice that there is no Shockley-James
paradox for the usual emf induced in closed circuits because these are
neutral.
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