MACS Monthly Newsletter - 2022 - AUG3

to be more than 15 psi or NO WATER WILL FLOW.
Let 's say, again for argument 's sake, that the pressure
at the pumping station is 30 psi. High pressure
will always try to equalize the low and that is what
is pushing the water out of the hose. If the pressure
outside the hose was greater than 30 psi, we
would actually force the water back up the hose to
the pumping station!
The DIFFERENCE, that 15 psi we would measure
between what is behind the water and what is outside
of the hose, is the pressure differential that is
causing the water to flow. That is voltage.
One more way just to make sure you've got this.
Consider how an engine breathes. As the piston
moves downward on its intake stroke, it creates a
vacuum. Vacuum is still a pressure. It 's just less than
atmospheric. Of course, on the outside of the engine's
air box is just that - atmospheric pressure.
When the intake valve opens, the high pressure on
the outside of the engine is going to try to equalize
the low pressure inside the cylinder, and air flows in.
If you were to connect a scan tool and read the MAP
(or Manifold Absolute Pressure) sensor reading, you
would read the difference between what is outside
and what is inside - the difference in pressure, the
difference in POTENTIAL, that is causing the air to
enter the engine. v
Current
Current is the movement of electrons through the
circuit. I'm no electrical engineer, as I mentioned
from the start, but I do know that current flow is
what does the work. It is the flow of electrical power
or charge and that is the definition of electricity. See
Figure 4.
In the water analogy I am working to debunk,
we were shown illustrations, even models, of water
flowing through a spinning wheel (representing
resistance) and a Gallons Per Minute gauge as an
example of current measurement. We saw electron
flow as starting at the battery, traveling through the
positive side of the circuit to the (fill in the electrical
component of your choice here) and back to the
battery. And even now, I still meet technicians that
describe current flow as little electrons following
the Yellow Brick Road (or Copper Brick Road if you
want) in an electrical circuit.
NO, this is not what 's happening.
Current flows at the speed of light, so for all practical
purposes, current flow is instantaneous when
the circuit is completed (more on that in a bit).
And it 's not one electron moving from the battery,
through the component, and back to the battery.
Think of it this way. Do you remember the fire brigades
of the old West? If a farmer's barn was on fire,
everyone in the community would form a line from
the closest water source to the fire, and back again.
The people in the line are atoms and the buckets
they are electrons that have been freed from the atoms.
The
atoms (in this case, the people) don't move.
August 2022
3
It 's the electrons (the
buckets) that move.
When one atom loses
an electron (hands off
his bucket),
it
is in a
state of imbalance and
is going to take an electron
from another atom
(the person before them
in line).
And each atom (person)
is trading off those
electrons (water buckets)
at the same time.
What we need to add
to this analogy is what
gets the electrons out
of balance to begin
with. Oh yeah - that 's
voltage! The difference
in electromotive
potential between the
start of the line and
the end of
the line. In
Figure 4: An amp clamp tool
like this one can make it easy
to find out how much current
is flowing through a wire. In
this case we're " clamped "
around the negative battery
cable (which is rather large),
but this technique also works
on small wires too.
the battery, that is the
positive and negative
posts. There are next
to no electrons on the
positive side and a butt
load of electrons on the negative side. They desperately
want to get to the side with no electrons and if
given a path, they will! And fast!
What slows them down, so they don't fry the wiring?
We're coming to that. In part, it 's limited by our
next topic. v
MACS Service Reports
Steve Schaeber
MACS Monthly Newsletter - 2022

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