More “teasers” for physics students? Suppose an electric circuit
(very complicated or very simple) is connected to a battery via two
wires, #1 and #2. We often say that in any short time interval the
current in wire #1 is equal to the current in wire #2. And some add
“because charges must be conserved”. Here are some questions.
An experiment was performed showing that I1 is largerthan I2.
And integrals of currents (when I1>0 and I2>0) differ in the same
way. For example, I1=5*I2 and Q1=5*Q2. Would such data be in
conflict with the law of conservation of electric charges? I do not
think so. By the way, the description of a real experiment of that
kind is going to be posted separately.
Suppose a circuit is very simple, only one branch, a vacuum
capacitor C (parallel plates very close to each other) in series
with R. Plus two ammeters, one inserted into the wire #1 and
another inserted into the wire #2; the R*C is conveniently
long. An experiment shows that I1=I2, at any moment. How
can it be if there is no motion of charges in the vacuum? The
displacement current through C was invented by Maxwell; is
it real or imaginary? These two adjectives are NOT used in
the context of complex numbers. An old question for each
generation of physicists and engineers.
Some say the displacement current is a mathematical
abstraction (extremely useful); it is not a real current. What
makes it less real than other abstractions, such as "ohmic
current" in a wire, or "water current" in a tube?