Previous in Forum: ATS Schematic Next in Forum: Corona Ring Manufacturers
Associate

Join Date: May 2009
Posts: 35

# Volts and Ohms

05/25/2009 8:37 PM

Not an engineer. I have spent a great deal of time trying to put a simple explanation of electricity on paper by looking at numerous internet sites. I can't seem to do it. You start out with coulombs which is straight forward. You add the time factor and get amps. After that everything seems to start becoming circular. You need volts to define ohms and you need ohms to define volts. (a clear definition of a joule [energy] without using watts [power] in the definition would also be nice since watts uses joules in its definition.) Can anybody make it clear? Thanks, Mike

Interested in this topic? By joining CR4 you can "subscribe" to

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Anonymous Poster
#1

### Re: volts and ohms

05/25/2009 10:25 PM

I take it you are trying to derive the foundations of SI units

http://physics.nist.gov/cuu/Units/units.html try this link, it has the basics, then followed by ones which can be derived from these and their derivation.

Associate

Join Date: May 2009
Posts: 35
#16

### Re: volts and ohms

05/26/2009 2:41 PM

I think that the formulas shown on the SI units site is probably what I was looking for although I was hoping there was something much simpler which I now think doesn't exist. I am familiar with the water flow analogy which is fine but I was looking for formulas but ones that I can understand. Many thanks to everyone who responded to my request. Mike

2
Power-User

Join Date: Jan 2008
Location: since 20 Jan 09, the USSA
Posts: 375
#22

### Re: volts and ohms

05/26/2009 11:15 PM

Don't give up so fast. Here's the analytical approach to deriving what voltage (actually electrical potential or tension) is. If you've had basic physics, you should be able to follow it. This is only for voltage, not resistance. Others did a very good job with that.

BTW, this convention of calling electrical potential or tension voltage is wrong. The unit of electrical potential/tension is the Volt. Calling electrical potential/tension voltage is like calling current amperage, or resistance ohmage. Just so you know.

Okay, here comes the analytical part.

You have charge and current correct. Current is the time rate of change of charge. Voltage (electrical potential/tension) is the driving force that causes current to flow.

Let's do a gravitational analogy to get a feel for what is happening, because it is very close.

You have Newton's law of gravitation.

F = G ME m / r2,

where F is the force of gravity, G is the gravitational constant, ME is the mass of the earth, m is the mass of an object attracted to the earth, and r is the separation.

If you want to figure out how a mass is accelerated in the earth's gravitational field, you can divide the above equation by the mass of the attracted object to find the force per unit mass exerted by the earth (acceleration due to earth's gravity):

g = F / m = G ME / r2.

In MKS units, G = 6.67 e-11 m3 / kg - s2, ME = 5.97 e 24 kg, and the radius of the earth is 6378 km.

If you plug that all in to the above equation, you get the familiar

g = 9.8 m / s2.

We are going to do the exact same thing with charges to get the same type of result.

Given two charges q1 and q2, separated by a distance r, the force between them is

F = k q1 q2 / r2,

where F is the force between the charges, and k is a constant whose value depends on the system of measurements chosen.

If you want to know the force per unit charge acting on a charge in the presence of charge q1, you divide each side of the above equation by q2:

F/q2 = k q1 / r2.

This is precisely analogous to the earth's gravitational acceleration, g, derived above. Where the computed earth's gravitational field is denoted "g", the electric force per unit charge is denoted E, for electric field:

E = F/q2 = k q1 / r2.

What we did at this point in the gravitational case analysis was to evaluate the value of the equation at a specific distance r, which was the radius of the earth, because that particular separation is of great practical importance. Because the radius of the earth is large compared to the "bumpiness" of the earth's surface, we may take the computed value "g" as a near constant working from the earth's surface all the way to low earth orbit (160 km up). Thus we can say that the gravitational potential difference between points at two different vertical heights is just the earth's field g, multiplied by the vertical separation, h:

gravitational potential = gh.

We do the exact same thing with electric charges.

If we evaluate

E = F/q2 = k q1 / r2

at some given value r1, we will get an electrical field "E" at that particular separation, due to charge q1 (analogous to the earth's gravitational acceleration "g"). If we then evaluate the electric field "E" at a separation r2 from q1 that is very nearly the same as r1, so that the E field value we calculated earlier doesn't change, we can simply multiply the E field value we calculated by the very small difference /r2-r1/ to determine the net potential difference between the two points that are r1 and r2 separated from q1. That potential difference has units of Volts.

So whereas

gravitational potential = gh,

electrical potential = V = Eh.

Now let's do some dimensional analysis.

From

E = F/q2 = k q1 / r2,

we can see that electric field has units of force per unit charge, or Newtons per Coulomb. From

electrical potential = V = Eh,

we can see that electrical potential has units of Newtons-meters per Coulomb. Now a Newton-meter is a Joule, the unit of energy, or work. So electrical potential has units of energy per unit charge. It follows that if we multiply electrical potential by charge, we should get work:

Energy = qV, or

Energy = qEh

Now let's jump back to the gravitational potential

gravitational potential = gh.

If we raise a mass m a height h in a gravitational field g, the energy acquired by the mass is:

Gravitational Potential Energy = mgh.

So finally, we have juxtaposed the two equations for gravitational and electrical potential:

Gravitational Potential Energy = mgh

Electrical potential energy = qEh = qV.

And the analogy is now complete. Just as height is proportional to gravitational potential energy in a constant gravitational field, electrical potential is proportional to energy in an electric field.

Associate

Join Date: May 2009
Posts: 35
#35

### Re: volts and ohms

05/27/2009 9:19 AM

Wow! This is going to take me a while. My son is studying engineering and I think he will sit down with me and go over this. Thank you much for the information. Mike

Guru

Join Date: Mar 2007
Posts: 2547
#2

### Re: volts and ohms

05/26/2009 12:31 AM

Can you look at it from as if it is a liquid?

A ml of water is a coulomb (say).

When it flows in a pipe (charge in an conductor) it is current.

For the flow to take place you need a pressure (that is the voltage)

When the flow s on, there is a friction in the pipe (resistance) that causes the pressure (voltage) to drop as you move along the pipe (same in electricity)

The energy required for this flow to take place is the energy (in KWH) and the power ie energy per second is the KW (it is the instantaneous value and is variable, and when summed up- integrated- over a time gives the total energy)

This is the basic (without units) the concept.

__________________
Fantastic ideas for a Fantastic World, I make the illogical logical.They put me in cars,they put me in yer tv.They put me in stereos and those little radios you stick in your ears.They even put me in watches, they have teeny gremlins for your watches
Anonymous Poster
#73

### Re: volts and ohms

01/10/2011 6:27 AM

this is a nice explanation. But when the pressure(voltage) drops , how does the flow (current) increases ??

Anonymous Poster
#74

### Re: volts and ohms

01/10/2011 12:24 PM

It doesn't. If you decrease the voltage the current decreases because the resistance remained the same.

If you apply 10 Volts to 100 Ohms you get 0.1 Amp.

If reduce to 5 Volts to 100 Ohms you get 0.05 Amp.

V/R=I

Anonymous Poster
#75

### Re: volts and ohms

01/10/2011 1:41 PM

Then y is this not holding true for transmission lines which are preferred in high voltage ? In HV lines, the current is low .. so they are preferred. but in the conductors, the resistance is going to be the same and when high voltage is applied shud we not have high flow of current or is ther any other concept to describe it ? i m in my high school n always had this doubt uncleared. also y do they hav "danger signs saying High voltage" when low voltage is supposed to have high currents (which i don understand why and hopin to get an answer fr it from the abov question.) ??

Anonymous Poster
#77

### Re: volts and ohms

01/11/2011 4:16 PM

Transmission lines are for transferring POWER. To transmit power at a low voltage it requires a high current and therefore a large conductor diameter. The same amount of power can be transmitted at a higher voltage and smaller current and therefore the same conductor diameter can be used to carry more power and the internal resistance of the conductor becomes less of an issue. With AC mostly the outer layer of the conductor is the path for current. If more power is needed more conductors can be added. Anything higher than 40 volts is considered hazardous. You need Danger Signs for safety reasons where higher voltages are present and people are able to come into contact.

2
Power-User

Join Date: Nov 2008
Location: Johannesburg
Posts: 295
#3

### Re: volts and ohms

05/26/2009 1:11 AM

Hi there,

Simply put,

The amount/rate of flow of electricity through the pipe - current.

The strength/force to push the current through the pipe - voltage.

The degree of difficuilty the current experiences to get through the pipe - resistance.

Hope this helps.

Regards,

Craig

Guru

Join Date: May 2007
Location: Harlow England
Posts: 16499
#4

### Re: volts and ohms

05/26/2009 3:50 AM

To continue the water analogy...
The cross sectional area of the pipe is the inverse of resistance..
Small bore pipe high resistance, big bore low resistance.
Just try changing you shower hose for a 5mm bore pipe and see what happens.

Gat a few component resistors, potentiometers, capacitors (100uF so you can see it charging on the meter) a 9v battery and a cheap digital meter.
Del

__________________
health warning: These posts may contain traces of nut.
Guru

Join Date: Mar 2007
Posts: 2547
#5

### Re: volts and ohms

05/26/2009 6:28 AM

And the accumulator is the capacitor. But I always fail to get what is an inductor- tries contant flow of current irrsepective of the voltage.

may be orifice?

__________________
Fantastic ideas for a Fantastic World, I make the illogical logical.They put me in cars,they put me in yer tv.They put me in stereos and those little radios you stick in your ears.They even put me in watches, they have teeny gremlins for your watches
Power-User

Join Date: Sep 2008
Posts: 196
#37

### Re: volts and ohms

05/27/2009 9:31 AM

Great discussion! Wouldn't a mechanical pressure regulator (pilot or spring operated) in a water line be a good analogy as compared to an electrical inductor? After all, an inductor simply opposes any sudden changes in current flow.

Guru

Join Date: Jan 2009
Posts: 1011
#44

### Re: volts and ohms

05/27/2009 3:52 PM

"an inductor simply opposes any sudden changes in current flow."

Any changes sudden or slow.

The point is that the inductor does that by storing energy in another form and retrieves it with little loss.
The capacitor is the pressure regulator and opposes a change in voltage (pressure) by low impedence to a change in electron charge accumulation.
The inductor is the current regulator and opposes a change in current converting it to a change in magnetic density. High Impedence to a change in magnetic field density.
Take a look at the way a CLC Pi filter works. The capacitors and inductor storage methods combine to cause phase shift to smooth the DC.

Power-User

Join Date: Aug 2008
Location: KY, USA
Posts: 367
#38

### Re: volts and ohms

05/27/2009 11:46 AM

A good fit for an inductor, both in function and in design, is a water wheel. Water hitting the blades of the water wheel loose some energy to push the wheel, so resistance is created. The rotational motion of the wheel can then be used to do work like an electric motor.

Another one is the heater coil. The coiled tubing adds length for resistance, and the transfer of heat can be used to do work. Plus, the coils of tubing are analogous to the coiled wire of an inductor.

__________________
The most valuable of all talents is that of never using two words when one will do. ~Thomas Jefferson
Guru

Join Date: May 2007
Location: Harlow England
Posts: 16499
#41

### Re: volts and ohms

05/27/2009 2:06 PM

hey, I like it...

__________________
health warning: These posts may contain traces of nut.
Off Topic (Score 5)
Power-User

Join Date: Aug 2008
Location: KY, USA
Posts: 367
#71

### Re: volts and ohms

06/29/2009 5:30 PM

Thanks - these comparisons may stretch the imagination a little, but I don't see any objections (which is pretty good when you post something in CR4).

__________________
The most valuable of all talents is that of never using two words when one will do. ~Thomas Jefferson
Off Topic (Score 5)
Commentator

Join Date: Mar 2008
Posts: 79
#55

### Re: volts and ohms

05/28/2009 2:31 PM

Inductance is the inertia of the water. If you slam the valve closed, you'll get a big spike in the pressure.

__________________
These little sayings down here are irritating. -- Me.
Guru

Join Date: Jan 2009
Posts: 1011
#59

### Re: volts and ohms

05/28/2009 4:09 PM

The stopping of flow from the source would allow the water to be released from the expansion tank representing the Magnetic field collapsing.

So when the flow is changed the expansion tank compression increases or decreases.

A short represented by stopping the flow at the load end would produce a high current / pressure spike like inertial hammering used in the Ram water pump.

This is where the diode/check valve could come into play to allow the high pressure spike to flow into a reservoir / Capacitor at a higher pressure and then block the return flow so the higher pressure water will flow to another storage component.

Guru

Join Date: Mar 2008
Location: Atlanta, Georgia
Posts: 749
#23

### Re: volts and ohms

05/26/2009 11:55 PM

Del,

You are so right and that is a good way, modeling the phenomena expressed by ohms law for real, to teach very young kids who have just gotten arithmetic, the connection to algebraic equations, something ostensibly they are not able to do until later.

j.

Power-User

Join Date: Nov 2008
Location: Johannesburg
Posts: 295
#6

### Re: volts and ohms

05/26/2009 6:39 AM

Hi SB,

Yes good anaolgy for an inductor. But would be a flow restriction orrifice.

Even better - self regulating flow control valve ;)

Regards,

Guru

Join Date: May 2007
Location: Harlow England
Posts: 16499
#7

### Re: volts and ohms

05/26/2009 7:17 AM

Surely an inductor is just a very long length of straight pipe...think of water hammer as the back emf?
Del

__________________
health warning: These posts may contain traces of nut.
Guru

Join Date: Mar 2007
Posts: 2547
#8

### Re: volts and ohms

05/26/2009 7:25 AM

self inductance ? (the orifice effect created by the length?)

__________________
Fantastic ideas for a Fantastic World, I make the illogical logical.They put me in cars,they put me in yer tv.They put me in stereos and those little radios you stick in your ears.They even put me in watches, they have teeny gremlins for your watches
Guru

Join Date: May 2007
Location: Harlow England
Posts: 16499
#9

### Re: volts and ohms

05/26/2009 7:31 AM

I see the mechanical analog of inductance as inertia...maybe I'm missing something but I don't see how an orifice is anything more than a resistance?
Maybe this needs a whole new thread?
I dunno I jus' a simple cat.
Del

__________________
health warning: These posts may contain traces of nut.
Guru

Join Date: Dec 2005
Location: Clemson, South Carolina
Posts: 1722
#18

### Re: volts and ohms

05/26/2009 4:29 PM

Length is a fair analogy. The dynamics of water flow are taken into account every time a main water line is designed. If anyone has ever seen an 8" elbow blown out (and what a mess it makes) would see the effects of flow stopping to suddenly.

Pressure spikes at a fast closing valve with a long run of pipe, just as the voltage across an inductor spikes when current is interrupted.

__________________
We have met the enemy and he is us . . . Walt Kelly
Commentator

Join Date: Mar 2008
Posts: 79
#56

### Re: volts and ohms

05/28/2009 2:34 PM

I'm with Del.

__________________
These little sayings down here are irritating. -- Me.
Anonymous Poster
#14

### Re: volts and ohms

05/26/2009 8:23 AM

Good analogy Del. That is the first time I heard a good sounding analogy for an inductor using the standard water circuit teaching aids. I may use that in the future to clarify how inductors work.

Power-User

Join Date: Nov 2008
Location: Johannesburg
Posts: 295
#10

### Re: volts and ohms

05/26/2009 7:48 AM

Hi all,

Usually a restriction orrifice is designed to keep the flow constant (in analogy the current constant) regardles of the pressure fluctuation (voltage).

It would be very interesting indeed to open a topic on this.

Regards,

Craig

Guru

Join Date: May 2007
Location: Harlow England
Posts: 16499
#11

### Re: volts and ohms

05/26/2009 7:54 AM

But an orifice only limits high flow/pressure, if you suddenly cut off the pressure or try to stop the flow it doesn't do much....
Wereas, you try stopping the current flow through an inductor...or the liquid flow through a loooooooong pipe, you can't do it easilly.

Del

__________________
health warning: These posts may contain traces of nut.
Guru

Join Date: Mar 2008
Location: Atlanta, Georgia
Posts: 749
#24

### Re: volts and ohms

05/27/2009 12:04 AM

You not thinking pussycat.

I think you know better. Must be late.

What you get across an inductor when you open the switch is the reverse emf caused by the falling magnetic field, not resistance of the original current flow.

j.

Guru

Join Date: May 2007
Location: Harlow England
Posts: 16499
#26

### Re: volts and ohms

05/27/2009 2:30 AM

'What you get across an inductor when you open the switch is the reverse emf caused by the falling magnetic field....'

Yes... which acts in a direction to try to maintain the original current flow...

'not resistance of the original current flow'.
I didn't mention the R word... I talked of 'inertia' which to my furry brain is a pretty good description of the phrase 'maintain the original current flow'.)
Anyhow...I'm happy to go with flow on this...it's not my party.

Del

__________________
health warning: These posts may contain traces of nut.
Guru

Join Date: Mar 2008
Location: Atlanta, Georgia
Posts: 749
#47

### Re: volts and ohms

05/27/2009 10:39 PM

Del, My humble apologies in advance for being an ass hole but, and this is what gets people to call me an ass hole, I am a stickler for the exactness of concepts.

Reverse EMF, and if it bites you or not is a function of the number of windings, is not the original current but rather a new flow in an opposite direction induced by the motion of the falling old current.

Again, Pussycat, my apologies. You are often amusing.

j.

Guru

Join Date: May 2007
Location: Harlow England
Posts: 16499
#51

### Re: volts and ohms

05/28/2009 3:38 AM

Indeed it is the collapsing doodab wot does it.
I think we are in danger of missing the point tho'...
Some people are delving into the maths, others into cause rather than effect.
Surely the point of an analogy is that it is a 'visual' (in your head) aid to understanding (rather than being an accurate model) of what is going on?
It's there to help us paint a mental picture which we can grasp...after all we know electrons aren't tiny blue balls, and the concept of 'lines of flux' always struck me as laughably archaic...but they help you visualise it.
Just think of the language we use... 'falling' current 'collapsing' magnetic field...all very emotive and visual...if we talked of 'high negative rate of change of flux density' people would fall asleep.
I did a thread about analogies yonks ago, as I think they are immensely valuable when they are good. I see them as small tasty helpful mice standing on my shoulder whispering advice...(just kidding).

Anyhow...it's an interesting topic.
Cheers

Del

__________________
health warning: These posts may contain traces of nut.
Guru

Join Date: Mar 2008
Location: Atlanta, Georgia
Posts: 749
#52

### Re: volts and ohms

05/28/2009 7:00 AM

Except for one small problem Dell,

The last time I placed a magnet under a sheet of paper of iron filings those "lines of flux" were real. Boring, perhaps, but all you need to perceive the real thing, real lines of flux, is a magnet and a sheet of paper with some iron filings.

Further, it is now possible to photograph stuff down to the molecular level, and you know what, those molecular structures are real just as we "modeled" them. Further, while the speed of those electrons around the nucleus is still too fast to stop photographically, you can see the path blurs where they are circling.

Look in a cloud chamber and you see the real paths of real sub-atomic particles, etc., etc.

That is the point of my remarks. Our models turn out to be real and while the math represents the abstract of those models and their functions, when you take these things apart with mental analogies based on the math, as opposed to the calculations which provide in the case of Ohms Law at least real material values, it tends to obscure the real image nature of things. It tends to imply that these things are not actually existent.

I've said this before. I don't know if here.

Ernst Mach, the Physicist and Philosopher, agreeing with Kant about not being able to know the thing in itself attempted to modernise Kant so that for Mach all that was available to us to know were complexes of sensations, i.e., tastes, smells, sounds, etc. Beyond that, he said, we cannot go. (An excellent work on the subject is V.I. Lenin's Materialism and Imperio-Criticism. If you are not into politics just pay attention to the conceptual argument which is what the bulk of the book is about.)

Forever kept from us were the things in themselves.

But, the fact is, that in recent years we have penetrated the things in themselves and through various extensions of our senses are able to see and photograph what before may have been expressed only as mathematical equations.

As an MRI machine examines the real time functioning of the human brain, or an electron microscope, or one of the even newer such thingies images the real micro world, all the old alleged barriers to our knowledge of the thing in itself are falling. The old mind/body duality apprehension (Or non-apprehension) has been destroyed and in fact we have not only Machs complex of sensations but images of the real thing in itself.

Hence, philosophy has been destroyed and we are left with science and the apprehension of a real material, concrete, knowable world. There is nothing else!

That is why I am such an asshole about accurate expression of concepts that are supposed to explain the real world.

j.

Guru

Join Date: May 2007
Location: Harlow England
Posts: 16499
#53

### Re: volts and ohms

05/28/2009 7:20 AM

We seem to be contriving to 'argue' about agreeing with eachother.
I don't think your 'lines' of flux are 'lines' at all they are not granular in fact 'lines of flux' is surely a contradiction as flux implies an amorphous continuum? The granularity is caused by the size of the iron filings.
Yes of course there is a field which has a shape and the 'lines of flux' idea helps us to visualise, plot and measure it.
Maybe we just end up discussing semantics?
The bottom line:-.... it is what it is...regardless of what we call it.
A rose by any other name would smell as sweet.
Anyhow, I've forgotten what we are discussing....
You are certainly no asshole, I think what we are also discussing is the appropriate level of an explanation to suit the target audience....which is often problematic and that takes us back to the power of analogies.
Using the water analogy to explain electricity to a 4year old (or a cat) would have both pro's and con's... but one would best avoid inductance entirely
Regards
Del

__________________
health warning: These posts may contain traces of nut.
Guru

Join Date: Feb 2008
Posts: 638
#54

### Re: volts and ohms

05/28/2009 8:12 AM

PFM

__________________
This moment is as it should be.
Guru

Join Date: Jan 2009
Posts: 1011
#62

### Re: volts and ohms

05/31/2009 9:38 PM

Hi Jack,

"The last time I placed a magnet under a sheet of paper of iron filings those "lines of flux" were real. Boring, perhaps, but all you need to perceive the real thing, real lines of flux, is a magnet and a sheet of paper with some iron filings."

The distribution of the filings is caused by the fact that they are all magnetically aligned in the same direction and repel each other. The alignment patterns however are due to the flux pattern. "Lines of force" are imaginary just like our water system representing the behavior of electricity. Or a stone idol to represent the gods of our imagination.

Would you rather be wet or electrocuted.

It is a fun excercise. Eh?

Jon

Guru

Join Date: Mar 2008
Location: Atlanta, Georgia
Posts: 749
#63

### Re: volts and ohms

06/03/2009 9:19 PM

Funny thing that!

When you move a wire in the lines of force represented by the iron filings flux pattern, somehow those imaginary lines of force generate a current or electron flow in the wire.

Or is all that just imaginary, i.e., the current in the wire, the electrons, etc.

Could it really be that the good Bishop Berkeley all those years ago was right? All that we imagine is real is only real insofar as it is real as a thought in the mind of god?

j.

Guru

Join Date: Jan 2009
Posts: 1011
#64

### Re: volts and ohms

06/03/2009 11:21 PM

The flux is real, the lines are imaginary and used only for the purpose of understanding the density, strength, polarity and alignment of the flux.

Nice philosophic touch.

Jon

Guru

Join Date: Mar 2008
Location: Atlanta, Georgia
Posts: 749
#67

### Re: volts and ohms

06/09/2009 1:13 PM

Then I imagine like the mind of god those lines indicated by the magnetic filings are only of our mind, not actually a material indication of the magnetic lines of flux?

Hence, a volt meter does not indicate the force of the flow of actual electrons, the ammeter does not indicate the actual volume of such flow, etc., etc., all that simply an expression of our mental imaging, not reality. Makes me wonder just what it is that a cloud chamber shows us in actuality?

That must mean we are like god. All this exists only because it exists as thought in our minds.

Sorry to belabor this but for me material reality and the expression of our mental imaging are usually one and the same and recent work imaging the heretofore impossible to image, has continuously demonstrated the validity of our conceptions of the materiality of our ideas right on down to the level of the atom.

I haven't researched it, meaning I have not sought here on the net where virtually everything is usually available, the original experiments that gave rise to the term "lines of flux" but I will make a bet that the term was coined in relation to iron filings on a sheet of paper over a magnet.

I first started playing with wires and batteries, magnets, iron filings and such carrying out the experiments in books written for such as I at eight or nine, i.e., 1942 0r 1943. Now, even down to the sub-molecular conjecturing of modern physics, even the rules as to right or left-handedness are supported in the math developed from actual experimentation.

Given the weird ideas that some of those same modern physicists come up with, as though opposed to Einsteins declaration that "god does not play at dice," I simply cannot pass by anything that questions the materiality of our ideas and our ability to accurately describe it.

Among those weird ideas is the assertion by some that the ideas we express are only mental conveniences, not reality, and that ala Kant we really "can't know the thing in itself."

I vehemently disagree with anything that smacks of such nonsense and with the advent of sub-atomic experimentation, let alone brain MRI's, etc., Kant was thoroughly discredited.

We can, and do indeed, know more and more about things in themselves.

j.

Guru

Join Date: Jan 2009
Posts: 1011
#69

### Re: volts and ohms

06/09/2009 1:54 PM

The SPACING of the filings is due to the fact that they are polarized in the same way and it forces them to repel each other and take positions based on their relative strength and their positions dont represent the graphic lines we use to represent them.

Their alignment is due to the magnetic field that we use graphics to represent. Rules of thumb are graphical representations of natural properties.

Nothing to get carried away about.

Power-User

Join Date: Nov 2008
Location: Johannesburg
Posts: 295
#12

### Re: volts and ohms

05/26/2009 8:07 AM

True,

But that is why I reccomended a self regulating flow control valve. This will keep the flow constant as long as there is pressure present.

Regards,

Craig

Anonymous Poster
#13

### Re: volts and ohms

05/26/2009 8:20 AM

But an inductor does allow the current to change. Itramps up or down based on the equation VL = L * di / dt (ideal with no resistance of course). So a constant flow regulator would hold a fixed current but would not act like an inductor experiencing a step change in voltage. I like Del's idea better, A sudden change in pressure at the inlet to the pipe would ramp up the flow rate based on the size of the step, the size of the pipe and the volume of water in it but like an inductor the flow would not change instantly.

Then again we will only get just so close explaining electricity with water in a pipe. Break the pipe the water still flows but break the wire and electricity stops (hopefully :-)

Guru

Join Date: Mar 2007
Posts: 2547
#15

### Re: volts and ohms

05/26/2009 9:08 AM

Here the break is a closed valve. It is not exactly similar you know, you are putting a high restriction to the flow (either current of electricity or water)

__________________
Fantastic ideas for a Fantastic World, I make the illogical logical.They put me in cars,they put me in yer tv.They put me in stereos and those little radios you stick in your ears.They even put me in watches, they have teeny gremlins for your watches
Commentator

Join Date: Mar 2008
Posts: 79
#57

### Re: volts and ohms

05/28/2009 2:52 PM

Let it go, craig. The flow control valve analogy is weak. An inductor is like a flywheel: resists speeding up as well as slowing down. Inertia is the analogous property.

__________________
These little sayings down here are irritating. -- Me.
Anonymous Poster
#17

### Re: Volts and Ohms

05/26/2009 4:25 PM

One of the instructors in a course that I attended a lot of years back liked the idea that there were only three effects involved in electrical circuits, Opens, Shorts and Resistance. Any of the others such as inductive reactance were resistance in a modified form. We couldn't figure out how to modify an open or a short so everything else seemed to be a form of resistance.

Power-User

Join Date: Oct 2008
Location: Meherrin Virginia
Posts: 319
#19

### Re: Volts and Ohms

05/26/2009 4:48 PM

An instructor of a course I attended had the opinion that there were only three effects involved in electrical circuits no matter how complicated the circuitry. They were the;

Open Circuit

Closed Circuit

Resistive Circuit

From that point you could make it as complicated as you wanted but in the end analysis a field effect transistor was only a controlled resistance, same is true with inductance, reactance, impedance ad nauseum.

Made sense to me at the time.

__________________
If you fail to follow through, you will fail.
Guru

Join Date: May 2007
Location: Harlow England
Posts: 16499
#20

### Re: Volts and Ohms

05/26/2009 6:02 PM

The instruxtor was an arse...
Obviously too thick to realise how much he didn't know
Del

__________________
health warning: These posts may contain traces of nut.
Commentator

Join Date: Mar 2008
Posts: 79
#58

### Re: Volts and Ohms

05/28/2009 2:55 PM

I'm with Del.

__________________
These little sayings down here are irritating. -- Me.
Guru

Join Date: Mar 2007
Posts: 2547
#21

### Re: Volts and Ohms

05/26/2009 10:05 PM

This is boiling down to the analogy of electrical and Fluid mechanics. So be it

hence

Diode = Non return (or Check valve)

Needle Valve os a rheostat or varistor?

Transistor =

SCR =

__________________
Fantastic ideas for a Fantastic World, I make the illogical logical.They put me in cars,they put me in yer tv.They put me in stereos and those little radios you stick in your ears.They even put me in watches, they have teeny gremlins for your watches
Guru

Join Date: Jan 2009
Posts: 1011
#27

### Re: Volts and Ohms

05/27/2009 2:47 AM

To continue:

This is boiling down to the analogy of electrical and Fluid mechanics. So be it

Hence:

For direct current:

Diode = Non return (or Check valve)

Needle Valve = rheostat - flow restrictor

Transistor = (transition resistor) flow restrictor or control valve. small energy

applied to control large energy.

SCR = pressure tripable valve. Like the pressure relief on your hot water heater.

Series capacitor = diaphragm - allows pressure measuring without letting liguid into the

gauge. Like the diaphragm in an expansion tank.

Parallel Capacitor = Storage reservoir for reducing variations in pressure.

(effectively low impedence)

Series Inductor = reduces variations in flow by storing it by converting it to air pressure

like in the expansion tank on top of your water heater for example.

(hi impedence)

Analog Mux = diverter valve

Anonymous Poster
#39

### Re: Volts and Ohms

05/27/2009 12:55 PM

Try these on for size:

Transistor = Regulator

SCR = Pilot Valve

Series Cap - Surge Tank

Parallel Cap = Accumulator

Anonymous Poster
#25

### Re: Volts and Ohms

05/27/2009 12:07 AM

My dad always explained it as a magical snake being jammed into a hole harder and harder as it grew stronger and the bite became harder the more it was compressed...

Then, just when you think you have it under control... It sneaks back and bites you.

Yeah.. I know.. It didn't help me either. But that's what it feels like when you get shocked. Okay, you had to be there.

JL Mealer

http://mealercompanies.com

Guru

Join Date: May 2007
Location: Harlow England
Posts: 16499
#29

### Re: Volts and Ohms

05/27/2009 3:21 AM

PMSL...
Priceless...that damn snake has bit me a few times.
Del

__________________
health warning: These posts may contain traces of nut.
Power-User

Join Date: Dec 2006
Posts: 408
#28

### Re: Volts and Ohms

05/27/2009 3:15 AM

There are many errors in the way electricity is presented. Electric flow can be pos-neg, or neg-pos, or stationary(ac). A more accurate way of describing Ef is charge sea. In a circuit, as many electrons leave as enter!. The movement of dc can be thought of as like putty. Narrowing a conductor results in speed up of charge sea flow!.

Guru

Join Date: Jan 2009
Posts: 1011
#30

### Re: Volts and Ohms

05/27/2009 3:26 AM

Man how things change!

S**t through a tin horn has become a politically correct foreign language.

Guru

Join Date: May 2007
Location: Harlow England
Posts: 16499
#31

### Re: Volts and Ohms

05/27/2009 3:37 AM

Is that errr, like... err... silly putty?

__________________
health warning: These posts may contain traces of nut.
Off Topic (Score 5)
2
Guru

Join Date: Mar 2007
Location: Greece / Athens
Posts: 722
#32

### Re: Volts and Ohms

05/27/2009 4:09 AM

Hi Mikesoneill. You said: "...After that everything seems to start becoming circular..."

There is no reason for all these confusion. Some concepts like "resistance" and "voltage", are connected to each other but they don't need each other in order to exist. I.e. the "voltage" exists without the need of "resistance" and vice versa.

The voltage on a point where is at a distance r from a point charge Q is V=k.Q/r (do you see anywhere the concept "resistance"?... no...)

The electric resistance of a metal conductor of length l and cross section S is R=ρ.l/S (do you see anywhere the concept "voltage"?... no...)

If you have two objects where the one has surplus of electrons and the other has lack of electrons then you have a voltage difference (i.e. potential difference) between them (again you don't see or use the concept "resistance"... ) Now, if you connect the two objects with a wire then a current flows through this wire for a while (due to the re-arrangement of the charges and re-establishment of balance) and its initial value is I=V/R (Ohm's law).

If you have a wire (with resistance R) and a current I flows inside this wire then a voltage difference is developed between its edges and its value is V=I.R (Ohm's law).

You see that (in both cases) the Ohm's law just "connects" these two individual (and otherwise independent) meanings.

Concerning the "electrical energy": it dosn't need the concept of "power" (e.g. it is E=q/4πεor). The "power" needs the concept of "energy" as it is the energy which is produced (or consumed) in 1 sec (i.e. 1W=1J/1sec).

I hope that I've helped you.

__________________
George
Guru

Join Date: Jan 2009
Posts: 1011
#40

### Re: Volts and Ohms

05/27/2009 1:28 PM

I didn't check to see if anyone mentioned this but:

Amps is volume of flow past a point over time.

Just sitting there is EMF

amps = actual number of electrons Hose= gallons of water in hose just sitting there

Guru

Join Date: Mar 2008
Location: Atlanta, Georgia
Posts: 749
#48

### Re: Volts and Ohms

05/27/2009 11:17 PM

Yeah George,

But despite all those nice abstractions in the math can you point to any actual electric circuit, outside of static electricity, where the circuit itself is not the resistance?

Now I'm going to stick my neck out by going from the very general of all phenomena, i.e., all things in motion, electricity is indeed the motion of electrons and when there is motion there is resistance, even for static electricity or a charged capacitor when you ground it or short it and dissipate the charge.

The concepts you are expressing may be helpful in understanding various aspects (Sometimes it is useful to look at a thing in their component parts even when they don't really exist except as concepts, I do it myself all the time) but nonetheless in the real world, if there is matter in motion there is resistance. If there is an electric circuit, i.e., electrons (Matter) in motion, there is resistance.

Without electron flow, there is only potential voltage (I deliberately put those two words together because we used to commonly call voltage "potential," anticipating its motion in a circuit), the voltage you would get out of a battery if you close a circuit from negative pole to positive pole.

Again, as I said to Dell, I am being an ass hole about exact concepts. My apologies.

j.

Associate

Join Date: Dec 2005
Posts: 39
#33

### Re: Volts and Ohms

05/27/2009 8:27 AM

Mike, just relax, and keep it simple. the analogy I use to help my supervisor is a garden hose.

volts = EMF (Electromotive force) Hose = pressure

amps = actual number of electrons Hose= gallons of water in hose just sitting there

ohms = resistance hose = size/ type of hose and nozzle

meter = test point in circuit Hose = bucket on ground

normally the bigger the hose (fire hose vs. garden hose) allows you to get more water into the bucket (amps) [High volume/low pressure]. if you put a nozzle (ohms) on the end, then you get more pressure, but the volume slows down.

Unless you are wanting heat or light as the end product,(toaster, heater, lightbulb) you do not want resistance (0hms). by the way, there is not an electrical engineer in the world that would not kill for EVERYTHING to be 'circular' as the more balanced a circuit (Circular) is the more efficient it is..

__________________
Life is a grinder, whether it wears you down or sharpens and polishes you up depends on what you're made of.
Power-User

Join Date: Mar 2006
Location: Valdosta, GA
Posts: 361
#34

### Re: Volts and Ohms

05/27/2009 9:07 AM

You are quite right about the "circular" part. For someone wanting a "simple" explanation you have chosen a complex subject it would seem. However, this may not be the case.

To start with, you have indicated an understanding of the concept of deriving amperage or current from the passing of a quantity of coulombs past a fixed point for a duration of time so, I will not address coulombs and all of it's complexities.

You state that "You need volts to define ohms and you need ohms to define volts" which is true if you know the resistance. If you don't know the resistance then neither of these would define the other without it. What you are dealing with here is a basic formula known as Ohm's Law: E=IR

This is as simple as it gets.

E = electromotive force = voltage = potential difference between two points.

R = resistance = the constant restriction of the flow of electrons in a circuit.

In order to know the value of an unknown quantity in this equation you must know the value of the other two quantities. To expound further would only complicate the issue.

As far as power is concerned: P=IE

P = Watts (Power)

I = Amperage (understood)

E = Voltage (electromotive force)

__________________
Always use protection.
Guru

Join Date: Mar 2008
Location: Atlanta, Georgia
Posts: 749
#49

### Re: Volts and Ohms

05/27/2009 11:50 PM

My, my.

I never dreamed of all the potential (Pun intended) analogies folks could dream up.

For instance seeing an inductor as equivalent to resistance which it may be but which has nothing to do with its primary purpose, i.e., transformer, alternator, motor, or clamp on sudden spikes, and which resistance is usually termed impedance to differentiate Alternating current flow resistance from Direct current insofar as the resistance of an inductor to AC is the result of its magnetic properties as opposed to simple resistance of direct current flow.

Very confusing all of these attempts, outside of the classic water flow ones, at analogies.

Leaving everything else out Keywalker gets it essentially right although even here I could quibble.

"This is as simple as it gets.

"E = electromotive force = voltage = potential difference between two points.

"R = resistance = the constant restriction of the flow of electrons in a circuit.

"In order to know the value of an unknown quantity in this equation you must know the value of the other two quantities. To expound further would only complicate the issue."

Indeed!

j.

Anonymous Poster
#36

### Re: Volts and Ohms

05/27/2009 9:22 AM

I don't know who your pupils will be, but this is what I do when I teach Amateur (ham) Radio to people.

I always use props. In this case, a piece of say 1/2 inch copper pipe, and a piece of say 2 inch PVC pipe, both a couple of inches long. I use a parallel between water flow through pipes as current, volts as the pressure, and a piece of smaller pipe as resistance. Then I demonstrate how filling a large water tank is similar to how electricity is measured in watt hours, after showing them how watts are calculated.

In our case columb of charge is not used, since this is basic electricity.

Hope that helps.

Terry Nixon

911 I.T. System Tech/ham radio operator

Power-User

Join Date: May 2008
Location: San Jose, CA, USA
Posts: 121
#42

### Re: Volts and Ohms

05/27/2009 2:41 PM

Mikesoneill,

There are following 7 basic magnitudes (units as per SI):

lenght: [m] meter

mass : [kg] kilogram

time : [s] second

electric current intensity: [A] ampere

thermodynamic temperature: [K] kelvin

amount of substance: [mol] mol

luminous intensity: [cd] candela

ALL other units are basically derived from those basic units:

i.e. volt [V] = (m^2 * kg)/s^3/A

ohm [..] = V/A = (m^2 * kg)/s^3/A^2.

Please see this site for a complete description

http://physics.nist.gov/cuu/Units/units.html

__________________
Scientes et audaces fortuna juvat !
Anonymous Poster
#43

### Re: Volts and Ohms

05/27/2009 2:56 PM

Math is incorrect.

Volt = kg m2 / Amp-sec

Ohm = Volt/Amp = kg m2 / A2 s

Reduction to this level is not terribly insightful. The earlier post that had the Volt per meter as a Newton per Coulomb, and the Volt as a Joule per Coulomb gives more physical insight.

Power-User

Join Date: May 2008
Location: San Jose, CA, USA
Posts: 121
#45

### Re: Volts and Ohms

05/27/2009 4:03 PM

I think it is correct:

kg*m2/sec2 => m*v2 = energy [J]

power = energy/time = J/sec

voltage = power/current => kg*m2/A/sec3.

similar for resistance.

__________________
Scientes et audaces fortuna juvat !
Anonymous Poster
#46

### Re: Volts and Ohms

05/27/2009 4:10 PM

You are correct about the fundamental units.

Power-User

Join Date: Dec 2006
Posts: 408
#50

### Re: Volts and Ohms

05/28/2009 2:21 AM

I agree that the simple way of describing "electricity" seems to work- however if you want an explanation of what really happens visit this site; BILL B ELECTRICITY ARTICLES http:amasci.com/ele-edu.html

Guru

Join Date: Jan 2007
Posts: 1024
#60

### Re: Volts and Ohms

05/29/2009 9:28 PM

A joule is a measurement of work done: (which creates heat etc)

a. A unit of electrical energy equal to the work done when a current of one ampere is passed through a resistance of one ohm for one second.

b. A unit of energy equal to the work done when a force of one newton acts through a distance of one meter.

The easiest way to understand electricity is the water analogy Think of water running down a hill

The height of the hill is the potential difference or Volts.

The volume of water flowing down the hill is the current.

The resistance the ground gives to the water is the ohms (opposite of slope. the opposite of ohms is called conductance)

The relationship of these three factors is called ohms law; E =I X R where;

E = potential difference measured in Volts

I = Current measured in Amperes R is resistance measured in Ohms

The formula follows normal math conventions and may be seen in different forms;

I =E/R

R=E/I

The simple definition of power in a Direct Current (DC) application is the ability to make work or E X I

It gets more complicated when you start talking Alternating current or AC Now you have to add frequency and its effects into the problem. In an AC circuit. Think of water in the ocean.

The height of the waves is the potential difference.

The amount of water moving is the current.

The slope of the wave affects the resistance of the current

With AC, there is a time factor where the current flows either before or after the peak of the wave. This is called the phase. If the wave peaks and starts to descend followed by the water flowing in the same direction, this is called a lagging phase. If the water moves before the wave peaks, it is called a leading phase. If the water moves the same time as the wave peaks, this is called unity power factor or 'in phase'

__________________
Perfection is a subjective and abstract concept.
Associate

Join Date: May 2009
Posts: 35
#61

### Re: Volts and Ohms

05/31/2009 3:39 PM

Thanks again to all who took the time to contribute to answering my question. The response was amazing and enlightening. Mike

Active Contributor

Join Date: Jan 2007
Posts: 23
#65

### Re: Volts and Ohms

06/05/2009 5:53 AM

The correct answer (engineering-scientific speeking) seems to be the following:

in 2004 year has been publisched a new innovative System of units named "Unified System for Gravitation and Electromagnetism", which is able to express all electromagnetic and gravitation units in the same common measure units: kilogram, metre/radian, second, wich purely are the basic/elementary units of the energy : Joule = kg.m^2/s^2 for translation movements; Joule = kg.m^2.rad^2/s^2 for spinnoid movements.

(Kenneth W. Parker, sea_kenp@mac.com)].

.

a)- The elementary electric charge (e) results quantitatively from the Momentum of the radial pulsatile mouvement of electron/positron's mass me, transmitted to the Quantum/Electromagnetic Physics Space (Q/E-PS), according to the relation:

e =(4π/3)mecc / kqα^2 = 1.60217653(14)x10^-19 [kg.m/s ≡ Coulomb],

where: cc= αc, is the electron's inner constituents/subparticles velocity; α is the Sommerfeld's constant (α = 1 / 137…); c is the light speed; α^2 is the energy conservative factor at genesis of cluster - electron, when the composing subparticles have pased from free-state at translation c velocity, to the cluster-state at both the subparticle-spinnoid c and the particle-spinnoid cc , velocities; kq is the refraction factor of the Q/E-PS, according to the relation:

kq =1- πα+ α / 2π =0.97842807(24)

b)- Amper = Coulomb/s ≡ kg.m / s^2 ≡ J / m, i.e. it is the force transmited from the pulsatile electron/positron, onto the Q/E-PS, during relative translation movement.

c)- Dielectric constant (εo) results quantitatively from the mass density of free subparticles of the Q/E-PS, which are dispersed by the pulsatile electrons/positron's translation movement, at the average radius re, according to the relation:

εo = me(4π/3kq )^2/4πre = 8.854187817...x10^-12 [kg./m≡Farad/m].

d)- The capacitive conductance results quantitatively from the radial electrons/positrons's mass overflow at pulsatile frequency fe , according to the relation:

e)- The magnetic permeability (μo) results quantitatively from the force which acts from the free subparticles of the Q/E-PS, at the c velocity, onto the spinoid cluster-electron/positron, according to relation:

1/μo = mec^2(4π/3kq)^2/4πre= 7.95774715(48)x10^5 [kg.m.rad/s^2 ≡ m/Henry]

resulting:

f)- The inductive conductance results quantitatively from the electrons/positrons's mass overflow at the spinnoid angular velocity ωe, according to the relation:

g)- The rezistive conductance of the Quantum/Electromagnetic Physics Space results quantitatively from the electrons/positrons's mass overflow permitted during the movement, according to the relation:

1/Zo=mec(4π/3kq)^2/4πre= 1/376.730313461 [kg/s≡ 1/Ohm].

h) The Volt = A.Ohm ≡ m / s , i.e. the cummulated (sinergycal) pulsatile velocity level of electron/positron's component subparticles.

i)- From the equivalences c) and f), results the known relation:

1/ μo εo =c^2

where c^2 is expressed in the unities:

which means the product of Q/E-PS's free components velocity (equal to the light velocity), and electron/positron's constituents spinnoid velocity, having ones origin from the genesis of cluster - electron, when the composing subparticles have pased from free-state at translation c velocity, to the cluster-state at both the subparticle-spinnoid c and the particle-spinnoid cc , velocities.

The Best Thinkings to All !

Iulian Somacescu

----------------------------------------------------------------------------------

To unifyed Gravitation and Electromagnetism, means to discover the same System of Units for both distinct Physics Spaces: Gravitatation(GS) and Electromagnetism(EMS). Up to day it's sufficiently proved: any other ways are pure useless speculative creations.

Guru

Join Date: Jan 2009
Posts: 1011
#66

### Re: Volts and Ohms

06/05/2009 6:46 AM

We were enjoying the simplicity of teaching the beginner how to play chopsticks on this piano made of paper and ink and you jumped in like Dinu Lipatti on a big Steinway grand piano.

Nice touch!

Guru

Join Date: Mar 2008
Location: Atlanta, Georgia
Posts: 749
#68

### Re: Volts and Ohms

06/09/2009 1:20 PM

Wait a minute!

The piano in front of me is not paper and ink but made out of glass, metals, phosphors and electrons.

j.

Guru

Join Date: Jan 2009
Posts: 1011
#70

### Re: Volts and Ohms

06/09/2009 1:59 PM

The point was "Chopsticks" versus "Warsaw Concerto"

That person is not into the difficult and complicated.

Guru

Join Date: Oct 2007
Location: Transcendia
Posts: 2963
#72

### Re: Volts and Ohms

06/29/2009 11:02 PM

Truly it is shocking I am still alive.

Still to get by, I like the water pipe analogies myself.

One of my earliest experiences with electricity was pissing on an electric fence.

Far as I can tell DC moves in the wire, and AC moves on the wire., and in either case bigger is better.

To paraphrase Epke, don't pee on the wires.

__________________
You don't get wise because you got old, you get old because you were wise.
Active Contributor

Join Date: Jan 2007
Posts: 23
#76

### Re: Volts and Ohms

01/11/2011 2:56 PM

Thanks to those who have challenged some fundamental scientific mysteries still remaining in the conventional knowledge of engineers today, and beyond.
In the kinetic relativity theory developed in the last 25 years, managed to express all the units of measurement used in physics, no matter the field, only by the four basic units of measure: kilograme, meter, radian and second (www.newinnovativesciencereview.eu ), has been shown that the kinetic equivalent of electric charge dimensions (Coulomb) are [kg*m*rad / s] and kinetic equivalent of electric current (Ampere) are [kg*m*rad / s2], respectively Ampere ≡ Newtons*radians (i.e. a tangential magnetic force which acts on electron during its continuous pulsating-spinne movement).
All experiences on electric-generators using rotating frame-conductor in magnetic fields, showed that the voltage generated is always proportional to the tangential speed of mobile electrons in the conductor rotates around the axis at an average distance rs and angular velocity ωs , according to the relation : U = ku*rss, where ku is a dimensionless constant which depends on conductor material and ratio of the stator magnetic field strength, on the one hand and intensity of the magnetic field generated by the rotation of electrons, on the other hand .
It results that the equivalent kinetic sizes of voltage is the tangential velocity of electrons during the rotation of the mobile circuit, i.e. [Volt ≡ m*rad / s].
All experiments conducted so far have shown that the electrical conductance of an electrical circuit (i.e. the inverse of electrical resistance) is always proportional to the mass flow of electrons that passes through the electrical conductor section (like electrical current).
The electrical conductance of the circuit being the ratio between Ampere and Volt, the kinetic equivalent sizes result: Mho = 1/Ohm ≡ A/V ≡ kg / s.
All the Best for All!
Iulian Somacescu
... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ...
Truly new and valuable things not find them never on beaten paths!

Interested in this topic? By joining CR4 you can "subscribe" to