On Thursday, February 27, 2014 10:11:23 PM UTC-6, Jim Wilkins wrote:
"Tom Gardner" Mars@Tacks wrote in message

news
On 2/26/2014 9:20 PM, RogerN wrote:

"Tom Gardner" wrote in message

...



Thanks for all the replies and knowledge. My other battery

charger is a

one pound electronic machine. It works OK, supplies 2, 6 and 12

amps and

has all sorts of buttons and lights! What it won't do is charge a

totally

dead battery...thus repairing the old Craftsman. It displays:

"BAD

BATTERY" and I have to hook-up jumper cables from another vehicle

to get a

few percent of a charge to get the electronic charger to work.



I also confess I don't know enough about electronics. Is there a

good book

to start with that isn't too stupid yet not over my head? I think

I can

still learn stuff.



Comparing to piping, hydraulics, fluidics, pneumatics...



Volts are pressure

Amps is flow

Resistance is opposition to flow, a restriction in the line.

Power (watts) is the product of flow and pressure.



Rectifiers are like check valves.

capacitors are like storage tanks, accumulators or air tanks.

transistors are like pilot operated valves



AC would be kind of like a piston pump with no check valves, the

power goes

one way and then the other.

So. using this back and forth fluid could drive a piston one size

that is

connected to a different size piston, either increasing pressure

and

decreasing volume, or increasing volume and decreasing pressure.

That would

be kind of like a transformer, it takes alternating current to make

it work.

So if you transformed your pumps force and pressure, it could be

changed

after the transformer by adding check valves at that point.



The old fashioned battery charger transforms the line voltage to a

lower

voltage at a higher current. Then a rectifier causes it to flow

only one

way into the battery.



Magnetic field going through a wire induces a voltage in the wire,

not sure

what that would compare to in hydraulics. The magnetic field

inducing

voltage has to do with transformers, motors, inductors, antenna,

and other.



RogerN









Good analogies Roger!



The water analogy of pressure = voltage, flow = current is useful when

you are first learning about Direct Current circuits, but it falls

apart quickly for Alternating Current because moving water's inertia

isn't the same as inductance, and we don't have the hands-on intuitive

experience with AC reversing flows that we do with DC garden hoses.



The analogy that helps me with AC is imagining the pistons and

crankshaft of an engine. The height of one piston represents the

constantly changing voltage of one phase of the power line. If it was

an equally spaced three-cylinder radial engine the other two pistons

would be the other phases. The three pistons (voltages) combine their

push in sequence to force a steady circular rotation of the

crankshaft, which was Tesla's inspiration for introducing AC to spin

motors without needing troublesome brushes.



This makes more sense if you understand sines and cosines.



Residential single-phase 120V is a one-cylinder engine and 240V is an

opposed twin, like a BMW motorcycle. Since they can hang at top dead

center they need a temporary circular push to start in the right

direction, the reason why single phase AC motors need starting

circuits but three phase ones don't.



.jsw

http://lpsa.swarthmore.edu/Analogs/E...alAnalogs.html