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More options Jan 20 2000, 3:00 am
Newsgroups: sci.electronics.basics
Date: 2000/01/20
Subject: Series circuit..water analogy...where does the water end up? Help please
In the water analogy of a series circuit, the water leaves the reservoir with
a high pressure and then goes through the pipes (wire) until it encounters and
lights up a lamp.

What happens to the water now?  Does it return to the battery or is it
consumed?

I can sense their might not be a quick answer here...any piece of the puzzle
would be appreciated.

Thanks!!

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More options Jan 20 2000, 3:00 am
Newsgroups: sci.electronics.basics
From: fdec...@aol.comNOSPAM (FDecker)
Date: 2000/01/20
Subject: Re: Series circuit..water analogy...where does the water end up? Help please
well, I guess you could picture a turbine there as the equivlent resistance in
your series circuit.  The force of the water is dissapated, but it flows right
back to the source.  Kirchoff's current law says the the some total off all the
currents flowing into a circuit, but flow out.  If there are no leaks in your
system, and nothing boils off as steam, all the water dribbles back to your
pump. :)

Voltage is lost, power is consumed, but current remains the same.  The
resistance determines the current.  Put another light in the circuit and the
total current goes down, in and out.  The water can't push in as hard when
there is more resistance down the line, but once it comes out the resistance it
keeps flowing at the same rate at which it went in.  You can think of it as if
it were a long string that you are pulling through a tube.  Squish the tube and
it is harder to pull the string, but all parts of the string move through the
tube at the same rate!

Fred - N4IXL

Please remember to remove the
<<NOSPAM>> from my email address

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More options Jan 20 2000, 3:00 am
Newsgroups: sci.electronics.basics
From: "Peter Russell" <p...@globalnet.co.uk>
Date: 2000/01/20
Subject: Re: Series circuit..water analogy...where does the water end up? Help please
not only does it return to the res. but it cannot flow until the return
connection is complete.

--
----

PeteR

pete <pch...@canada.com> wrote in message

news:g_Hh4.4865\$mK.310965@brie.direct.ca...

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More options Jan 20 2000, 3:00 am
Newsgroups: sci.electronics.basics
From: Patrick Timlin <ptim...@yahoo.com>
Date: 2000/01/20
Subject: Re: Series circuit..water analogy...where does the water end up? Help please

> In the water analogy of a series circuit, the water leaves the
> reservoir with a high pressure and then goes through the pipes
> (wire) until it encounters and lights up a lamp.

> What happens to the water now?  Does it return to the battery
> or is it consumed?

Think of it this way. You have a system which is filled with water. You
have a pump that moves (circulates) the water through the system and
then you have a "load" which the current of water makes do something.
You used a light, so we'll stick with that. So with your system, you
turn on the pump and the water is circulated through the pipes, through
the light which causes it to turn on and then back to the pump again to
continue circulating. You are adding energy to the system through the
pump. In this case you use electricity to make the pump circulate the
water thus converting the energy into the flow of water. The light uses
this energy by taking it back out of the system, converting it to
light. So energy into your system via the pump and back out via the
light.

Now I think were you might be getting confused when you think of
electricity is the common misconception that you have these little
electronics flowing out of the postive side of your (for example)
battery carrying little packages of energy which are then used in the
light, then the little electron travel back to the negative side of the
battery empty handed without that energy. This is what often confuses
students since this sort of makes sense on one hand, but then again, if
it really worked that way, what is different about the electrons before
the light and those after? Well nothing! They are electrons after all,
a charged particle. They don't lose their charge and they certainly
were not carrying little bundles of energy.

Instead, and this is were many books and professors fail to make it
clear to students, you have to think of the system as a whole. You add
energy to the WHOLE system at the same time with the battery and take
it out of the WHOLE system with the light.

One great way I heard it explained once that really made it clear to me
is to think of a bicycle wheel. Flip the bike over. Now you grab the
peddle with your hand and get the wheel going really fast. You added
energy to the system by turning the crank. Now, put your hand on the
tire to slow it down. Your hand gets hot and you remove energy from the
system through friction with your hand. Now, when you put your hand on
the wheel, did the part of the wheel after your hand slow down while
the part before your hand was still travelling faster? Of course not!
Just like when you spin the pedel, part of the wheel doesn't start
moving first while other parts stay still until the whole wheel is
turning either. In both cases the WHOLE wheel speeds up or slows down.
You are adding and removing energy from the WHOLE wheel, not just the
part under your hand.

Yes, the energy removed is concentrated at your hand in the form of
friction, or in the case of a circuit, at the light bulb. This is where
the energy comes out, but as you hopefully can now see, you removed
that energy from THE SYSTEM as a whole, not from just those electronics
coming though the lamp at that moment.

I hope that made sense.

--
Patrick Timlin --- ptim...@yahoo.com
http://www.geocities.com/ptimlin/

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More options Jan 20 2000, 3:00 am
Newsgroups: sci.electronics.basics
From: Peter Bennett <pete...@interchange.ubc.ca>
Date: 2000/01/20
Subject: Re: Series circuit..water analogy...where does the water end up? Help please

On Thu, 20 Jan 2000 18:05:48 GMT, pch...@canada.com (pete) wrote:
>In the water analogy of a series circuit, the water leaves the reservoir with
>a high pressure and then goes through the pipes (wire) until it encounters and
>lights up a lamp.

>What happens to the water now?  Does it return to the battery or is it
>consumed?

It returns to the reservoir.

Be careful when using this (or any other) analogy.  Analogys are often
good for explaining a particular concept, but may fail completely with
related cncepts.

Electric current always flows in a complete circuit - from one
terminal of a voltage source, through the load, and back to the other
terminal of the source.  The current is the same at all points in a
series circuit.

--
Peter Bennett VE7CEI
GPS and NMEA info and programs: http://vancouver-webpages.com/peter/index.html
Newsgroup new user info: http://vancouver-webpages.com/nnq

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More options Jan 20 2000, 3:00 am
Newsgroups: sci.electronics.basics
From: rbmccam...@mmm.com (Roy McCammon)
Date: 2000/01/20
Subject: Re: Series circuit..water analogy...where does the water end up? Help please

pete wrote:

> In the water analogy of a series circuit, the water leaves the reservoir with
> a high pressure and then goes through the pipes (wire) until it encounters and
> lights up a lamp.

> What happens to the water now?

a pump returns it to the reservoir.

Opinions expressed herein are my own and may not represent those of my employer.

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More options Jan 20 2000, 3:00 am
Newsgroups: sci.electronics.basics
From: daniel fodor <fa...@catskill.net>
Date: 2000/01/20
Subject: Re: Series circuit..water analogy...where does the water end up? Help please
I don't see any fault with the water analogy. The water returns to the resevoir
either through the ground, or it evaporates and falls back to the resevoir as
rainfall.

Dan Fodor

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More options Jan 21 2000, 3:00 am
Newsgroups: sci.electronics.basics
From: Science Hobbyist <bbe...@microscan.com>
Date: 2000/01/21
Subject: Re: Series circuit..water analogy...where does the water end up? Help please
In article <g_Hh4.4865\$mK.310...@brie.direct.ca>,

> In the water analogy of a series circuit, the water leaves the
reservoir with
> a high pressure and then goes through the pipes (wire) until it
encounters and
> lights up a lamp.

Not exactly.  There is no resevoir.  The "water" is not provided
by the battery, instead it is provided by the wires.  Don't forget,
in the Water Analogy, we use pre-filled pipes.  In real wires,
the "stuff that flows" is provided by the atoms of the metal.
All metals everywhere contain a sort of "electron fluid."

It's a very common misconception that batteries supply the
"water." Instead, batteries act as charge pumps: they take in
electrons through one lead, and they spit out the same number
of electrons through the other lead.  The total number of
electrons inside the battery never changes.  However, a
battery certainly does perform work.  It PUSHES charges through
itself, and this causes all of the electrons in the external circuit
to begin flowing too.

If batteries never lose any electrons, why do they run down?
Simple answer: they run out of fuel.  A battery is a chemically-
powered charge pump.  When the "fuel" chemicals have all been
converted into waste products, the battery stops working.
And, when we "recharge" a battery, we are simply running a
chemical reaction backwards.  The waste products are turned back
into "fuel" chemicals, and it takes energy to do this.

It might help if you mentally get rid of the battery, and replace
it with a DC generator.  What's inside a DC generator?  Wires.
There's no place for electrons to build up or be stored.  This
mental image helps to defeat the incorrect idea that "power
supply" means "provider of electrons."  In reality, a power
supply is an electron pump, not an electron source.

Another water analogy: imagine that a battery is like a pump
that's driven by a spring-driven wind-up motor.  It can only pump
water until its spring unwinds.  To wind it back up, force the water
to flow backwards through it.  Energy is stored in the "spring".
The water columns inside the hoses can be used to transmit energy,
but the water is obviously not energy, right?  This leads to
a major insight:

ELECTRICITY IS NOT A FORM OF ENERGY!

Am I totally crazy?  No.  Think about it.  Batteries don't
store electrons, and when a battery is "charged",it has just as
many electrons as when it is "dead."  Also, electrons flow around
and around the circuit, and the circuit never loses or
gains electrons.  Knowing these facts, how could anyone EVER claim
that a flow of electricity is a flow of energy?  Yet textbook
after textbook says that electricity is energy.  This is terrible!
It prevents everyone from understanding the simple basic facts
behind simple circuits.

> What happens to the water now?  Does it return to the battery or is
it
> consumed?

The water is pumped THROUGH the battery and back out through the
other terminal.  When a real battery operates a real circuit, there
is an electric current in the water between the battery plates
as well as in the connecting wires. (In other words, "complete
circuit" means just what it says, and the path for current
also includes the electrolyte of the battery.) Yes, the current in
the electron is composed of moving ions and not moving
electrons.  Nevertheless, it is an electric current (it is a flow
of charges.)

> I can sense their might not be a quick answer here...any piece
> of the puzzle would be appreciated.

For a huge mass of "electricity rants", see:

ELECTRICITY MISCONCEPTIONS ARTICLES
http://www.amasci.com/ele-edu.html

--
((((((((((((((((((( ( (  (   (    (O)    )   )  ) ) )))))))))))))))))))
William Beaty                                 bbe...@microscan.com
Software Engineer                             http://www.microscan.com
Microscan Inc., Renton, WA                    425-226-5700 x1135

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More options Jan 21 2000, 3:00 am
Newsgroups: sci.electronics.basics
From: kins...@frognet.net (Mark Kinsler)
Date: 2000/01/21
Subject: Re: Series circuit..water analogy...where does the water end up? Help please

>Am I totally crazy?  No.  Think about it.  Batteries don't
>store electrons, and when a battery is "charged",it has just as
>many electrons as when it is "dead."  Also, electrons flow around
>and around the circuit, and the circuit never loses or
>gains electrons.  Knowing these facts, how could anyone EVER claim
>that a flow of electricity is a flow of energy?

Because it's the flow of charge, which can quite reasonably be called
"electricity," that transfers the chemical energy of the battery to the
heat energy of the lightbulb.  The electron stream acts like a drive
shaft, and it's not unreasonable to think of energy flowing through a
driveshaft.  Sort of.

>Yet textbook
>after textbook says that electricity is energy.  This is terrible!

That's because textbooks have a rather loose definition of "electricity."
Alfred North Whitehead addressed the difficulty: "Electricity isn't a
_thing_.  It's the way things behave."

>It prevents everyone from understanding the simple basic facts
>behind simple circuits.

Well, yeah.  The problem is that science books are written by people
without a lot of love for the physical sciences.  Apparently they figure
they can sublimate their fear of things like electric power and
telecommunications theory by establishing lots of focus groups.

I've had difficulty with the hydraulic analogy because it turns out that
people don't know any more about plumbing than they do about electricity.

M Kinsler
--
........................................................................... .
114 Columbia Ave. Athens, Ohio USA 45701 voice740.594.3737 fax740.592.3059
Home of the "How Things Work" engineering program for adults and kids.
See http://www.frognet.net/~kinsler

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More options Jan 21 2000, 3:00 am
Newsgroups: sci.electronics.basics
From: "Ken" <a...@b.com>
Date: 2000/01/21
Subject: Re: Series circuit..water analogy...where does the water end up? Help please
I too, really like the water analogy.  I'm just a hobbiest, and these
comments are a big help to me.

Can you give me your thoughts on these analogies:
power source = water pump
resistor = bottle neck in the pipe line. (voltage decrease?)
diode = allows water to pass through in only one direction, the valve will
close if water tries to go in the opposite direction.
transistor = valve that has two sources of water that can combine to produce
a higher volume of water (voltage increase?).  If the base has no water,
then the collector does not flow.
capacitor = Reservoir that will allow a steady supply of water to pass
through, but will not allow a fluctuating supply to pass.
choke or inductor = freely allows water to pass until too much water comes
through, if too much comes through, it will close the gate.

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More options Jan 21 2000, 3:00 am
Newsgroups: sci.electronics.basics
From: Peter Bennett <pete...@interchange.ubc.ca>
Date: 2000/01/21
Subject: Re: Series circuit..water analogy...where does the water end up? Help please

On Fri, 21 Jan 2000 11:24:33 -0700, "Ken" <a...@b.com> wrote:
>I too, really like the water analogy.  I'm just a hobbiest, and these
>comments are a big help to me.

>Can you give me your thoughts on these analogies:
>power source = water pump
>resistor = bottle neck in the pipe line. (voltage decrease?)
>diode = allows water to pass through in only one direction, the valve will
>close if water tries to go in the opposite direction.
>transistor = valve that has two sources of water that can combine to produce
>a higher volume of water (voltage increase?).  If the base has no water,
>then the collector does not flow.

I'd say the collector-emitter path is a valve that is controlled by
the water flow in the base-emitter path - the more flow in the base,
the farther open the valve is pushed.

>capacitor = Reservoir that will allow a steady supply of water to pass
>through, but will not allow a fluctuating supply to pass.

Someone previously described a cpacitor as a chamber with a rubber
diaphram across it - water can flow in from either side, and stretch
the diaphram, pushing water out the other side, but can't flow trough
it.

>choke or inductor = freely allows water to pass until too much water comes
>through, if too much comes through, it will close the gate.

No - it would have to be something that allows a continuous flow (DC),
but provides opposition to changing flow.  Possibly a paddlewheel in
the pipe, with a flywheel on it?

--
Peter Bennett VE7CEI
GPS and NMEA info and programs: http://vancouver-webpages.com/peter/index.html
Newsgroup new user info: http://vancouver-webpages.com/nnq

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More options Jan 21 2000, 3:00 am
Newsgroups: sci.electronics.basics
From: Patrick Timlin <ptim...@yahoo.com>
Date: 2000/01/21
Subject: Re: Series circuit..water analogy...where does the water end up? Help please

"Ken" <a...@b.com> wrote:
> Can you give me your thoughts on these analogies:
> resistor = bottle neck in the pipe line. (voltage decrease?)

Or how about a valve?

> transistor = valve that has two sources of water that can combine
> to produce a higher volume of water (voltage increase?). If the
> base has no water, then the collector does not flow.

One of those water bed filler/drainer devices. <grin>

> capacitor = Reservoir that will allow a steady supply of water to
> pass through, but will not allow a fluctuating supply to pass.

No, a capacitor (in a series circuit) tends to block DC (steady
current) and pass AC (alternating current). In parallel, maybe you can
think of a capacitor like a storage tank or pressure tank on a private
well system.

Don't forget the pipes themselves. Pipes = Wires. Like water pipes, the
more current flow you are going to need, the larger the wires you need.

--
Patrick Timlin --- ptim...@yahoo.com
http://www.geocities.com/ptimlin/

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More options Jan 21 2000, 3:00 am
Newsgroups: sci.electronics.basics
From: "Ken" <a...@b.com>
Date: 2000/01/21
Subject: Re: Series circuit..water analogy...where does the water end up? Help please
I can understand the resistor, diode, and transistor just fine.  But I'm
having problems with the Capacitor and inductor.

> Someone previously described a cpacitor as a chamber with a rubber
> diaphram across it - water can flow in from either side, and stretch
> the diaphram, pushing water out the other side, but can't flow trough
> it.

Does that mean that water cannot flow through.  ie. no current can pass
through a capacitor? That doesn't make sense.

And what is the difference between a polarized capacitor (electrolitic) and
non-polarized (ceramic).

> >choke or inductor = freely allows water to pass until too much water
comes
> >through, if too much comes through, it will close the gate.

> No - it would have to be something that allows a continuous flow (DC),
> but provides opposition to changing flow.  Possibly a paddlewheel in
> the pipe, with a flywheel on it?

So it opposes any change in current, but does not oppose a direction (like a
diode).  ie.  It keeps all current at constant levels.  I don't know what
you mean by paddlewheel and flywheel.
(or does it oppose voltage change, not current change??)

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More options Jan 21 2000, 3:00 am
Newsgroups: sci.electronics.basics
From: Peter Bennett <pete...@interchange.ubc.ca>
Date: 2000/01/21
Subject: Re: Series circuit..water analogy...where does the water end up? Help please

On Fri, 21 Jan 2000 14:46:59 -0700, "Ken" <a...@b.com> wrote:
> I can understand the resistor, diode, and transistor just fine.  But I'm
>having problems with the Capacitor and inductor.

>> Someone previously described a cpacitor as a chamber with a rubber
>> diaphram across it - water can flow in from either side, and stretch
>> the diaphram, pushing water out the other side, but can't flow trough
>> it.

>Does that mean that water cannot flow through.  ie. no current can pass
>through a capacitor? That doesn't make sense.

Yes - direct current cannot flow through a capacitor.

Actually, that water anology is not too bad for describing the action
of a bypass capacitor, but doesn't really apply to coupling (DC
blocking) capacitors (same part, different use)

>And what is the difference between a polarized capacitor (electrolitic) and
>non-polarized (ceramic).

The construction of an electrolytic cap allows a much greater capacity
for a given voume than ceramic or other non-polarized construction.

>> No - it would have to be something that allows a continuous flow (DC),
>> but provides opposition to changing flow.  Possibly a paddlewheel in
>> the pipe, with a flywheel on it?

>So it opposes any change in current, but does not oppose a direction (like a
>diode).  ie.  It keeps all current at constant levels.  I don't know what
>you mean by paddlewheel and flywheel.

An inductor opposes a change of current through it (and a capacitor
opposes a change of voltage across it)

I was thinking of a paddlewheel in the pipe that would be turned by
the water passing by.  A flywheel on the same shaft (outside the pipe)
would limit any change in the speed or direction of rotation of the
paddlewheel, thereby limiting a change in speed or direction of water
flow.

The water analogy may be useful in describing some aspects of
electricity, but it breaks down for others.

--
Peter Bennett VE7CEI
GPS and NMEA info and programs: http://vancouver-webpages.com/peter/index.html
Newsgroup new user info: http://vancouver-webpages.com/nnq

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More options Jan 21 2000, 3:00 am
Newsgroups: sci.electronics.basics
From: s...@stdavids.marconimed.com (Sam Goldwasser)
Date: 2000/01/21
Subject: Re: Series circuit..water analogy...where does the water end up? Help please
In article <dqeh8sg8ek75msp370q6anvh5bg255h...@4ax.com> Peter Bennett <pete...@interchange.ubc.ca> writes:

>   >choke or inductor = freely allows water to pass until too much water comes
>   >through, if too much comes through, it will close the gate.
>   No - it would have to be something that allows a continuous flow (DC),
>   but provides opposition to changing flow.  Possibly a paddlewheel in
>   the pipe, with a flywheel on it?

Actually, the water itself has 'inductance'.  The 'water hammer' effect
is the result of a sudden change in flow rate.  That air trap is just a
snubber. :)

--- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html

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More options Jan 22 2000, 3:00 am
Newsgroups: sci.electronics.basics
From: Peter Lawton <peter_john.law...@virgin.net>
Date: 2000/01/22
Subject: Re: Series circuit..water analogy...where does the water end up? Help please

Mark Kinsler wrote:
> That's because textbooks have a rather loose definition of "electricity."
> Alfred North Whitehead addressed the difficulty: "Electricity isn't a
> _thing_.  It's the way things behave."

Does the word have any meaning in Science at all?
Is it not a word existing only in 'maninthestreetspeak'?
The man in the street uses it with his customary lack of precision when
he means any of electrical energy, electrical power or electric charge.
An interesting point is that he also happily practises Orwellian style
'doublethink' for although only electric charge of these three may be
considered a 'thing', people are quite convinced that electricity IS a
thing - usually measured in MW, although amps or volts can do just as
well.
As a secondary school teacher, I know that pupils doggedly hold on to
their pr-(mis)conceptions. They won't believe me if I say the word has
no precise meaning -the TV announcer uses it and he has far more
credibilty than I.
Accepting that 'electricity' can not be removed from pupils'
vocabularies,
I make the best of a bad job and embrace the word for the closest
quantity in physics to their already existing concept - that closest
quantity I suggest being electric charge.
As a rider I freely admit that after two years of my teaching it to
them, hardly any pupil has much more idea of it than when they started.
But I don't think I am alone in this. After all, everyone (in the UK at
least) has studied 'electricity' ('oops - I'm using IT as the name of a
subject now) at school. Yet how many have a clue?

Peter Lawton

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More options Jan 22 2000, 3:00 am
Newsgroups: sci.electronics.basics
From: kins...@frognet.net (Mark Kinsler)
Date: 2000/01/22
Subject: Re: Series circuit..water analogy...where does the water end up? Help please

>>> Someone previously described a cpacitor as a chamber with a rubber
>>> diaphram across it - water can flow in from either side, and stretch
>>> the diaphram, pushing water out the other side, but can't flow trough
>>> it.

>>Does that mean that water cannot flow through.  ie. no current can pass
>>through a capacitor? That doesn't make sense.

>Yes - direct current cannot flow through a capacitor.

But alternating current can.  It stretches the rubber diaphragm in one
direction, pushing water out the other side.  When the pressure reverses,
the flow reverses.  If the diaphragm is stretched such that the pressure
against it equals the pressure of the supply, then the water flow will
stop.

>Actually, that water anology is not too bad for describing the action
>of a bypass capacitor, but doesn't really apply to coupling (DC
>blocking) capacitors (same part, different use)

It can certainly apply to a blocking capacitor.  The DC component will
stretch the diaphragm a considerable amount, and the AC signal component
will make the diaphragm deflect a bit in either direction from that
stretched position.  Remember that there's water on each side of the
diaphragm, so the AC variations will be transmitted through the capacitor.

>The water analogy may be useful in describing some aspects of
>electricity, but it breaks down for others.

The inductor works pretty well, too.  Think of a very long pipe filled
with water.  Put that in your circuit.  You'll find that the inertia of
the water therein prevents you from either starting or stopping the flow
of water as quickly as you might wish.  Thus the current has a tendency to
stay constant and free from quick variations.

We can even make hydraulic transformers.  These consist of two
different-diameter cylinders containing pistons joined by a common
connecting rod.  A lot of fluid entering the big cylinder at low pressure
will eject a small amount of fluid at high pressure from the small
cylinder.  These are used quite a lot in hydraulic systems and they
correspond 1:1 with electric transformers.

M Kinsler

--
........................................................................... .
114 Columbia Ave. Athens, Ohio USA 45701 voice740.594.3737 fax740.592.3059
Home of the "How Things Work" engineering program for adults and kids.
See http://www.frognet.net/~kinsler

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More options Jan 22 2000, 3:00 am
Newsgroups: sci.electronics.basics
From: "Ken" <a...@b.com>
Date: 2000/01/22
Subject: Re: Series circuit..water analogy...where does the water end up? Help please

Patrick Timlin <ptim...@yahoo.com> wrote in message

news:86ak2c\$m6e\$1@nnrp1.deja.com...

> Don't forget the pipes themselves. Pipes = Wires. Like water pipes, the
> more current flow you are going to need, the larger the wires you need.

btw.  Is it ok to replace a small wire with a larger one in an old device?
It should be, since the same current can flow.

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More options Jan 22 2000, 3:00 am
Newsgroups: sci.electronics.basics
From: "Ken" <a...@b.com>
Date: 2000/01/22
Subject: Re: Series circuit..water analogy...where does the water end up? Help please

Mark Kinsler <kins...@frognet.net> wrote in message

news:pH9i4.19626\$pb2.1633381@tw11.nn.bcandid.com...

> >>Does that mean that water cannot flow through.  ie. no current can pass
> >>through a capacitor? That doesn't make sense.

> >Yes - direct current cannot flow through a capacitor.

> But alternating current can.  It stretches the rubber diaphragm in one
> direction, pushing water out the other side.  When the pressure reverses,
> the flow reverses.  If the diaphragm is stretched such that the pressure
> against it equals the pressure of the supply, then the water flow will
> stop.

OK. that makes sense.  But why would you want AC to flow and not DC?  I can
understand DC because everything flows in a particular direction.  But when
you have AC in a circuit, it throws me off.

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More options Jan 22 2000, 3:00 am
Newsgroups: sci.electronics.basics
From: Patrick Timlin <ptim...@yahoo.com>
Date: 2000/01/22
Subject: Re: Series circuit..water analogy...where does the water end up? Help please

"Ken" <a...@b.com> wrote:
> btw.  Is it ok to replace a small wire with a larger one in an old
> device? It should be, since the same current can flow.

Yep, works fine. If your choice of replacing a wire is between one that
is smaller and one that is larger, then always go for the larger to be
safe.

--
Patrick Timlin --- ptim...@yahoo.com
http://www.geocities.com/ptimlin/

Sent via Deja.com http://www.deja.com/

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More options Jan 22 2000, 3:00 am
Newsgroups: sci.electronics.basics
From: kins...@frognet.net (Mark Kinsler)
Date: 2000/01/22
Subject: Re: Series circuit..water analogy...where does the water end up? Help please

>> But alternating current can.  It stretches the rubber diaphragm in one
>> direction, pushing water out the other side.  When the pressure reverses,
>> the flow reverses.  If the diaphragm is stretched such that the pressure
>> against it equals the pressure of the supply, then the water flow will
>> stop.

>OK. that makes sense.  But why would you want AC to flow and not DC?  I can
>understand DC because everything flows in a particular direction.  But when
>you have AC in a circuit, it throws me off.

Many devices which handle communications signals convert these into a
varying DC voltage.  For example, the output of an audio amplifier which
uses a 12v power supply might be about 9 volts plus-or-minus 1 volt.  That
means that the output voltage varies between 8 volts and 10 volts.  The
variation contains our sound signal, while the 9 volts it varies around is
an artifact of the amplifier itself.

We generally analyze such a signal by thinking of it as a DC voltage
combined with an AC voltage.  In this case, we have a 1v AC voltage
(i.e., plus-or-minus one volt) superimposed upon a 9 v DC voltage. We can,
and often do, consider the AC and DC components separately.

Now, if we were to apply this signal to a loudspeaker, we would find that
the 9v component would cause the speaker's voice coil to conduct a lot of
current and overheat.  Thus we'll use a "blocking capacitor" in series
with the amplifier.  This will allow only the _variations_ in the signal
to go through the speaker.

M Kinsler

--
........................................................................... .
114 Columbia Ave. Athens, Ohio USA 45701 voice740.594.3737 fax740.592.3059
Home of the "How Things Work" engineering program for adults and kids.
See http://www.frognet.net/~kinsler

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More options Jan 23 2000, 3:00 am
Newsgroups: sci.electronics.basics
From: "Fred Decker" <fdec...@compuserve.com>
Date: 2000/01/23
Subject: Re: Series circuit..water analogy...where does the water end up? Help please
You know, all this analogy stuff is clever, but why not try to understand
the actual theory of the operation of the device.  I think that is better
anyway.  Start off with a good understanding of charges.  Like charges
repel, opposites attract.  Now picture little electrons, all with a negative
charge moving in one direction, creating a hole or positive charge in it's
wake moving in the other direction that another electron can fill.

A capacitor, in it's simples form, is just two conducting plates separated
by an insulator.  You apply a current and for a time, there is one, as all
the little electrons start stacking up on the plate and through their charge
creating a positive charge on the other plate.  As soon at the capacitor can
take no more charge, the current stops and there you are with a big charged
capacitor.

If this was an AC current so that you reverse the polarity at your battery
and the current would flow right back in the other direction.  If the value
of the capacitor and frequency of the AC current are correct, they you can
flip back and forth all day long charging and unchanging the capacitor and
it will act like it isn't even there.  But here is the cool part, lower the
voltage, and the charge on the capacitor plates leak back into the circuit
and it keeps the voltage steady.  Small variations in voltage aren't noticed
because the capacitor acts like a little backup battery.  That is why we say
a capacitor resists a change in voltage.  Picture the voltage stored as
surplus as a charge on those plates, and you will always remember RESISTS A
CHANGE IN VOLTAGE.

Now an inductor is a coil of wire, basically an electromagnet.  You can
think of all those curled up wires as resisting the flow of current in your
head without much imagination, but lets see what happens.  Current flows in
the wire.  Each wire sets up a magnetic field created by the electric field
flowing through it,  these little magnetic fields all interact between each
loop of wire.  As you flow current into an inductor, it also stores a
charge, although unlike the capacitor, it is only for the time current is
flowing.  This magnetic field impedes the flow of electrons or the current
in order to propagate itself.  Picture a bunch of turns of wire around a
nail and just by connecting them to a battery, you can pick up metal
objects.  Disconnect the battery and the  objects are released.  Work is
being done somewhere.

Here is the cool part about electrons.  The current is impeded as the field
builds up on the inductor coil.  As soon as you disconnect the power, the
field collapses and the moving magnetic lines of force create an electric
current in the wire.  So you can see here that changes in current are
resisted because as the current changes, the magnetic field stored in the
inductor can pump some back into the circuit.  You can think of the inductor
as a generator that can supply current back into the circuit.  I think the
flywheel analogy is pretty good.

The real advantage to AC is that it can be TRANSFORMED.  If you needed 115v
of DC at your outlet instead of AC, how would we get it to you?  We would
either have to send you 115 volts, or send a higher voltage, heating up all
the wires, and then waste more energy with resistors to drop the voltage
down at your house.  Losses in the power lines because of resistance would
be so great, we would have to have a power station on every corner.  With
AC, we can send hundreds of thousands of volts on a line, so that if we lose
10%, who cares?  Then we transform it down to tens of thousands of volts,
then at the pole going into your house to 240 or 120 or whatever.  Then we
transform it back to DC to run all the electronics in your house except for
heating elements and electric motors.

Your last question about why would we want AC to flow and not DC, is getting
into applications.  You really will have to get into putting components
together and learn progressively to understand that.  It is like you are
asking about calculus and we are just now learning addition and subtraction.
You have to build to that point and be patient.

Capacitors provide several functions, one is to prevent the flow of DC.  You
might want an audio signal, for example, to be amplified, but want to remove
the DC component of that signal.  If you couple two stages of a circuit with
the right capacitor, an AC (audio, radio, etc.) would pass as if the
capacitor wasn't even there, but DC would be blocked.  You can also filter
things.  You wouldn't want to short out your circuit by connecting a
positive voltage source directly to ground, but you could do just that with
a capacitor.  DC would not flow through the capacitor, but certain AC
frequencies could.  That is how the bass and treble controls in a stereo
work.  You pass certain frequencies and block others with resistors and
capacitors.

Keep plugging.  You probably already have head several breakthroughs.
Electronics is like that, you hit a plateu and stay frustrated for a while,
then when you breakthrough it is a major leap and if seems like dozens of
things make sense all of a sudden... until the next wall. :)

Fred

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More options Jan 24 2000, 3:00 am
Newsgroups: sci.electronics.basics
From: kins...@frognet.net (Mark Kinsler)
Date: 2000/01/24
Subject: Re: Series circuit..water analogy...where does the water end up? Help please

>A capacitor, in it's simples form, is just two conducting plates separated
>by an insulator.  You apply a current and for a time, there is one, as all
>the little electrons start stacking up on the plate and through their charge
>creating a positive charge on the other plate.  As soon at the capacitor can
>take no more charge, the current stops and there you are with a big charged
>capacitor.

Be careful here.  There is, theoretically, no limit to the amount of
charge a capacitor can store as long as its dielectric doesn't break down.
A capacitor stops charging when the voltage developed across it from the
stored charge equals the voltage of the source that's providing that
charge.

>If this was an AC current so that you reverse the polarity at your battery
>and the current would flow right back in the other direction.  If the value
>of the capacitor and frequency of the AC current are correct, they you can
>flip back and forth all day long charging and unchanging the capacitor and
>it will act like it isn't even there.

The frequency is not at all critical.  Any capacitor will pass an
alternating current at any frequency.

>But here is the cool part, lower the
>voltage, and the charge on the capacitor plates leak back into the circuit
>and it keeps the voltage steady.  Small variations in voltage aren't noticed
>because the capacitor acts like a little backup battery.  That is why we say
>a capacitor resists a change in voltage.  Picture the voltage stored as
>surplus as a charge on those plates, and you will always remember RESISTS A
>CHANGE IN VOLTAGE.

That's a perfectly good model, but it's not always helpful in every case.

>Now an inductor is a coil of wire, basically an electromagnet.  You can
>think of all those curled up wires as resisting the flow of current in your
>head without much imagination, but lets see what happens.  Current flows in
>the wire.  Each wire sets up a magnetic field created by the electric field
>flowing through it,  these little magnetic fields all interact between each
>loop of wire.  As you flow current into an inductor, it also stores a
>charge, although unlike the capacitor, it is only for the time current is
>flowing.  This magnetic field impedes the flow of electrons or the current
>in order to propagate itself.

It's probably better to think of an inductor as an electric generator that
produces a voltage that opposes any change in the current flowing through
it.  Electrical inertia is a good model for this.

>Picture a bunch of turns of wire around a
>nail and just by connecting them to a battery, you can pick up metal
>objects.  Disconnect the battery and the  objects are released.  Work is
>being done somewhere.

The only work done is when the objects are moved or released, and that
has little to do with the self-inductance of the system.  An inductor
stores and releases energy, ideally in equal measure.

>Here is the cool part about electrons.  The current is impeded as the field
>builds up on the inductor coil.  As soon as you disconnect the power, the
>field collapses and the moving magnetic lines of force create an electric
>current in the wire.  So you can see here that changes in current are
>resisted because as the current changes, the magnetic field stored in the
>inductor can pump some back into the circuit.  You can think of the inductor
>as a generator that can supply current back into the circuit.  I think the
>flywheel analogy is pretty good.

Yup.  Inertia.

M Kinsler

--
........................................................................... .
114 Columbia Ave. Athens, Ohio USA 45701 voice740.594.3737 fax740.592.3059
Home of the "How Things Work" engineering program for adults and kids.
See http://www.frognet.net/~kinsler

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More options Jan 24 2000, 3:00 am
Newsgroups: sci.electronics.basics
From: Peter Lawton <peter_john.law...@virgin.net>
Date: 2000/01/24
Subject: Re: Series circuit..water analogy...where does the water end up? Help please

Mark Kinsler wrote:
> It's probably better to think of an inductor as an electric generator that
> produces a voltage that opposes any change in the current flowing through
> it.  Electrical inertia is a good model for this.

Yes. How about thinking of an inductor as a region where the 'effective
mass' of the electron fluid is increased. In regard to this, does a
single electron have inductance? It certainly has mass, so accelerates
at non infinite rate, stores energy (kinetic) and carries on once the
accelerating force is removed.
Does the inductance of say a wire consist of two parts - one due to the
'real' mass of the charges and the other due to their magnetic
interaction which increases their 'effective' mass?
And I think of a capacitor plate as a region where the compressibility
of the electron fluid is increased (by the cancellation of the electric
fields of each plate by that of the other). So large amounts of this
fluid can be added or subtracted with less than the usual pressure
increase. The electrons can be packed more densly or more easily
removed.
One proton and one electron make a capacitor perhaps?
Peter Lawton

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More options Jan 24 2000, 3:00 am
Newsgroups: sci.electronics.basics
From: anti.s...@netcentral.co.uk (Martin Pickering {UK})
Date: 2000/01/24
Subject: Re: Series circuit..water analogy...where does the water end up? Help please

"Ken" <a...@b.com> wrote:
> I can understand the resistor, diode, and transistor just fine.  But I'm
>having problems with the Capacitor and inductor.

>> Someone previously described a cpacitor as a chamber with a rubber
>> diaphram across it - water can flow in from either side, and stretch
>> the diaphram, pushing water out the other side, but can't flow trough
>> it.

>Does that mean that water cannot flow through.  ie. no current can pass
>through a capacitor? That doesn't make sense.

You just *might* find the explanation at my web site useful. It's rather
basic and uses the dreaded water analogy but I've had good comments from
some people who say it helps. It has the advantage of using pretty pictures
which are much easier to understand than words :o)

Martin Pickering
http://www.satcure.co.uk

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