25)
The above expression is used to define the ampere (A), which is one of
the seven SI base units *
It turns out that when we have time-dependent currents and/or charges in
motion, Newton’s third law may not hold for forces between charges and/or
conductors An essential consequence of the Newton’s third law in mechanics
is conservation of momentum of an isolated system This, however, holds even
for the case of time-dependent situations with electromagnetic fields, provided
the momentum carried by fields is also taken into account