Answer 1:
The
electric current in a conductor is
proportional to a quantity called the
drift velocity, which is the average
velocity of the electrons in the conductor.
In a conductor without an applied electric
field (for example, a piece of wire with no
battery connected to it), the drift velocity is
zero. This is because the electrons are, on
average, not moving in any particular
direction. [Note that the electrons are still
moving, and at very high speeds, but they rebound
off of the atoms in the conductor at random angles
which average out to no motion.] Upon
application of a voltage, there is then a
push toward motion in one direction through the
conductor, a
non-zero drift velocity proportional to the
applied voltage is attained, and current flows
in the conductor.
Since the current is a result of a net electric
field in a particular direction, speeding or
slowing the current can be achieved by increasing
or decreasing the magnitude of that field.
Electric fields follow the principle of
superposition, so increasing or decreasing
the field requires creating another electric
field in the same location. As hinted in the
question, fluctuating magnetic fields induce
electric fields in conductors (typically called an
electromotive force, EMF, in this
context). This is
Faraday's Law.
Magnetic fields also follow
superposition, so 7 individual fluctuating
magnetic fields around the circuit results in a
single net fluctuating magnetic field, and a
single net EMF. The direction of the EMF
depends on the change in the flux and follows
Lenz's Law.
Whether the EMF causes the current to flow
faster or slower will thus depend on the direction
of the magnetic field and the direction of change
of that field (so it will reverse at times
with the fluctuation). Realize that a field other
than the induced EMF does not need to be present
in the circuit. If this is the case, then the
rate of current flow without the magnetic fields
is zero, and faster or slower will depend
solely on the induced EMF.
Note that the principles in this question are
essentially those governing operation of DC
generators and motors, except that the
question has the magnetic fields fluctuating
rather than the conductor moving ("fluctuating")
through fixed magnetic fields.
Here is a video which clearly explains how
these generators and motors work. (The video is
old and long, but it is still one of the best I
have found. A shorter one can be found
here. )
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