Why no Residential Fridges?

[valhalla360]

Originally Posted by sailorchic34

But to get the storage capacity required in gallons of storage you must know the GPM or GPH flow rate required. In the case of the big prime movers they would run 24/7 so easy to define. Otherwise its a WAG or wild A$$ guess.

You keep arguing against the use of amp-hrs but then your examples keep proving my point.

You need both the flow rate and duration. Together for electricity that translates to amp-hrs.

[valhalla360]

Originally Posted by newhaul

Actually most engines are referred to by their displacement ( call a parts house and say you need parts for a 185 HP Chevrolet engine they will say what engine but if you say a 307 they will know exactly what engine (307 cubic inch displacement)

That's what I said. I abreiviated cubic centimeter to cc.

And yes, the standard for parts is to call out the displacement but the average new car buyer could care less about the displacement. They care about HP.

But to take your example a 307 sounds like a bigger number than a 185.

[Wotname]

Originally Posted by svlamorocha

The dimensional formula you are referring to will depend on the unit system. In SI a coulomb is defined as an ampere times one second, with both ampere and second being base units. In cgs system the (stat)coulomb is a base unit.

You can make the comparison helpful by considering the analogy between:

- a coulomb is equal to 6240000000000000000 electrons, while
- a gallon of water has 1270000000000000000000000000 electrons.

The difference is that with the water you also get some protons and neutrons thrown in

Originally Posted by valhalla360

Forgive me if I'm just enjoying the discussion at this point as the original question is long since answered.

I'm plagerizing a bit from the National Institute of Standardsand Technology website but:

Using SI (Système International [d'Unités]), everything boils down to
a combination of the fundamental units- meter, gram, second, ampre, kelvin, mole, candela.

The rest are derived units. To define a quantity of electricity, Coulomb is derived by the dimensions: Amp-Sec. Thus it is not a dimensionless quantity.

Since the typical cruiser has easier access to both the amperage and duration using the fundamental units is more convienent. (with the minor discrepency of using hours instead of seconds).

Well, others have a different view

I note there are many simple "definitions" of a coulomb in googleland but IMO, one should dig deeper.

A coulomb can be described as 1 amp.second and it is the equivalent to 1 amp.sec but it isn't fundamentally defined as such.

From the Encyclopaedia Britannia.
The unit of electric charge in the metre–kilogram–second and SI systems is the coulomb, equivalent to the net amount of electric charge that flows through a cross section of a conductor in an electric circuit during each second when the current has a value of one ampere. One coulomb consists of 6.24 × 1018 natural units of electric charge,such as individual electrons or protons
and
Many fundamental, or subatomic, particles of matter have the property of electric charge

The bit in red strongly suggests that a coulomb is simply a specified number of natural units - thus dimensionless.

And from WhatIs.com
The coulomb (symbolized C) is the standard unit of electric charge in the International System of Units (SI). It is a dimensionless quantity, sharing this aspect with the mole.

Now these sources may not be the most rigourous of scholarly papers but they do match what I learnt decades back doing an electrical degree. Perhaps the world has moved on or perhaps we are only looking at simplified aspects of the subjects these days...

[valhalla360]

Originally Posted by sailorchic34

Oh Dear me




To your other question,



How many GPH does a 20 liter jerrycan hold? Somewhere between 0 and 4.45 ish.


.

So you are saying your 20 liter jerrycan, let's call it a 5 gallon can to avoid confusion converting from liters to gallons (then again most 20liter cans actually hold a little more than 5 gallons so no worries about overfilling if we put 5 gallons in your 20 litter can) holds 0GPH to 4.45GPH...ish.

I repeat...your 5 gallon can holds at most 4.45GPH based on your statement. For some inexplicable reason it may hold as little as 0GPH.

So does that mean you can't fill your jerry can with a hose that puts out more than 4.45GPH, since it maxes out at 4.45GPH? That seems rather difficult to accomplish since the slow gas pumps put out upwards of 2000-3000GPH. High speed pumps for the big offshore power boats put out much more.

You jerry can has an inderterminant volume, yet it is still rated at 5 gallons? Why is it, I've never seen a can with a rated capacity of 5GPH (or any GPH rating)?

You must be hated as the gas dock. At best it's going to take you over an hour to fill up ONE jerrycan. Maybe more if you aren't running close to the 4.45GPH. God forbid you have 3 or 4 jerry can's to fill.

Since you claim to have an engineering background, please tell us you are just yanking our chain. I'm trying not to be rude but shouldn't be a difficult concept for someone with a basic engineering background.

[a64pilot]

Have any of you guys watched the Big Band Theory where Sheldon and Leonard are having a conversation, but neither is listening to the other ?

[valhalla360]

Originally Posted by Wotname

Well, others have a different view

I note there are many simple "definitions" of a coulomb in googleland but IMO, one should dig deeper.

A coulomb can be described as 1 amp.second and it is the equivalent to 1 amp.sec but it isn't fundamentally defined as such.

From the Encyclopaedia Britannia.
The unit of electric charge in the metre–kilogram–second and SI systems is the coulomb, equivalent to the net amount of electric charge that flows through a cross section of a conductor in an electric circuit during each second when the current has a value of one ampere. One coulomb consists of 6.24 × 1018 natural units of electric charge,such as individual electrons or protons
and
Many fundamental, or subatomic, particles of matter have the property of electric charge

The bit in red strongly suggests that a coulomb is simply a specified number of natural units - thus dimensionless.

And from WhatIs.com
The coulomb (symbolized C) is the standard unit of electric charge in the International System of Units (SI). It is a dimensionless quantity, sharing this aspect with the mole.

Now these sources may not be the most rigourous of scholarly papers but they do match what I learnt decades back doing an electrical degree. Perhaps the world has moved on or perhaps we are only looking at simplified aspects of the subjects these days...

Interestingly, I found several sources that call an amp the fundamental unit for charge and coulumb defined by it. Including the origianl govt SI site I quoted. An official SI site would seem to have more credence than "whatis.com" in my mind.

The again, many of the fundmental units have been redefined based on atomic measurements A meter is a particular distance traveled by a photon in a period of time when originally it was intended to be 1/10,000,000 of the distance from the equator to the pole. Until they found out that earth isn't a perfect sphere, so the redefined it as a piece of metal then as they needed more accuracy, they went to the atomic based measurement.

Please explain how something can be dimensionless if it is defined by two dimensions that are not the same. Ie:
- Time/Time is dimensionless as the dimensions cancel out (anything divided by itsel is 1)
- Gal/Hr has dimensions.

[valhalla360]

Originally Posted by a64pilot

Have any of you guys watched the Big Band Theory where Sheldon and Leonard are having a conversation, but neither is listening to the other ?

Yes, but that doesn't matter because I'm right.

[StuM]

If you are going to quote authorities, it really helps if you provide the URL so that others can fact check!
Fact checking your sources reveals a slightly different picture to what you have represented.

Originally Posted by Wotname

Well, others have a different view

I note there are many simple "definitions" of a coulomb in googleland but IMO, one should dig deeper.

A coulomb can be described as 1 amp.second and it is the equivalent to 1 amp.sec but it isn't fundamentally defined as such.

From the Encyclopaedia Britannia.
The unit of electric charge in the metre–kilogram–second and SI systems is the coulomb, equivalent to the net amount of electric charge that flows through a cross section of a conductor in an electric circuit during each second when the current has a value of one ampere. One coulomb consists of 6.24 × 1018 natural units of electric charge,such as individual electrons or protons
and
Many fundamental, or subatomic, particles of matter have the property of electric charge

The bit in red strongly suggests that a coulomb is simply a specified number of natural units - thus dimensionless.

That is NOT an accurate quote from Encyclopedia Britannica here:

coulomb | unit of energy measurement | Britannica.com
which actually says:

"Coulomb, unit of electric charge in the metre-kilogram-second-ampere system, the basis of the SI system of physical units. The coulomb is defined as the quantity of electricity transported in one second by a current of one ampere. Named for the 18th–19th-century French physicist Charles-Augustin de Coulomb, it is approximately equivalent to 6.24 × 1018 electrons. See electric charge."

The Definition as stated is 1 Ampere second. The actual wording of the sentence which corresponds to your highlighted section contains the word "approximately" and is therefore certainly not a definition.

And from WhatIs.com
The coulomb (symbolized C) is the standard unit of electric charge in the International System of Units (SI). It is a dimensionless quantity, sharing this aspect with the mole.

Now these sources may not be the most rigourous of scholarly papers but they do match what I learnt decades back doing an electrical degree. Perhaps the world has moved on or perhaps we are only looking at simplified aspects of the subjects these days...

Then fact checking at Whatis.com we have:
Table of Physical Units - Reference from WhatIs.com
where we find:
"charge quantity ( Q ) coulomb (C)" under the table of Derived Units.

So your first authority actually does define charge quantity as Amp seconds and your second reference, assuming your quote is correct, has two opposing definitions which suggests that it is not a very good authority.

[jhnhll]

FWIW This is an amp. Keeps me charged for about three hours. It does flow though. Have never measured the flow on the other end.


Sent from my iPhone using Cruisers Sailing Forum

[StuM]

Oh, just spotted another misconception:

"The bit in red strongly suggests that a coulomb is simply a specified number of natural units - thus dimensionless."

Dimensionless doesn't mean a number of natural units. If it is defined in term of a single natural unit, then that has one dimension. A dimensionless number is just that - a bare number such as Reynold's number,specific gravity, pH or 42. It doesn't have any "dimension" or "natural unit".

[newhaul]

Originally Posted by jhnhll

Attachment 110549
FWIW This is an amp. Keeps me charged for about three hours. It does flow though. Have never measured the flow on the other end.


Sent from my iPhone using Cruisers Sailing Forum

And those amps come in various colors and flavors
Also you can use the residential fridge on your boat to keep them cold so they taste better.

[sailorchic34]

Originally Posted by StuM

Oh, just spotted another misconception:

"The bit in red strongly suggests that a coulomb is simply a specified number of natural units - thus dimensionless."

From Wikipedia,

"Dimensionless doesn't mean a number of natural units. If it is defined in term of a single natural unit, then that has one dimension. A dimensionless number is just that - a bare number such as Reynold's number,specific gravity, pH or 42. It doesn't have any "dimension" or "natural unit".

Oddly Dimensionless, means it does not have length, but you can still count them, very much like electrons pass through a wire.

Even though a dimensionless quantity has no physical dimension associated with it, it can still have dimensionless units. To show the quantity being measured (for example mass fraction or mole fraction), it is sometimes helpful to use the same units in both the numerator and denominator (kg/kg or mol/mol).

The quantity may also be given as a ratio of two different units that have the same dimension (for instance, light years over meters). This may be the case when calculating slopes in graphs, or when making unit conversions. Such notation does not indicate the presence of physical dimensions, and is purely a notational convention. Other common dimensionless units are % (= 0.01), ‰ (= 0.001), ppm (= 10−6), ppb (= 10−9), ppt (= 10−12), angle units (degrees, radians, grad), dalton and mole. Units of number such as the dozen and the gross are also dimensionless."

So the number of electrons passing through a wire is dimensionless, but they are never the less actual units.

[sailorchic34]

Originally Posted by valhalla360

So you are saying your 20 liter jerrycan, let's call it a 5 gallon can to avoid confusion converting from liters to gallons (then again most 20liter cans actually hold a little more than 5 gallons so no worries about overfilling if we put 5 gallons in your 20 litter can) holds 0GPH to 4.45GPH...ish.

I repeat...your 5 gallon can holds at most 4.45GPH based on your statement. For some inexplicable reason it may hold as little as 0GPH.

So does that mean you can't fill your jerry can with a hose that puts out more than 4.45GPH, since it maxes out at 4.45GPH? That seems rather difficult to accomplish since the slow gas pumps put out upwards of 2000-3000GPH. High speed pumps for the big offshore power boats put out much more.

You jerry can has an inderterminant volume, yet it is still rated at 5 gallons? Why is it, I've never seen a can with a rated capacity of 5GPH (or any GPH rating)?

You must be hated as the gas dock. At best it's going to take you over an hour to fill up ONE jerrycan. Maybe more if you aren't running close to the 4.45GPH. God forbid you have 3 or 4 jerry can's to fill.

Since you claim to have an engineering background, please tell us you are just yanking our chain. I'm trying not to be rude but shouldn't be a difficult concept for someone with a basic engineering background.

The question was how many gph it can hold, not how fast you can fill it.

Sorry, I never flll jerry cans full as I can't lift a full jerry can.
As to 0 GPH, that would be when it's empty.

[sailorchic34]

Originally Posted by StuM

It's the RATE at which electrical charges pass through a point/cross section of the conductor where RATE and SPEED are synonymous. (And electrical charges are Coulombs). It is not speed of motiion, it is speed of energy flow.l

Lets reread the sentence:

Current does not have to do with how far charges move in a second but rather with how many charges pass through a cross section of wire on a circuit.

It's how many electrons that carry pass through a cross section of wire, not how fast they pass through a cross section of the wire. Quantity passing is not at all the same as speed of passing. Quantity is a rate but it's not a speed. It's not speed of energy flow as that is measured by drift rate

Electrons entering a wire do not travel the length of the wire. when they enter a wire, they push another different electron out the other end. It's not quite that simple, but for this discussion it's close enough.

So electrons don't speed through the wire in any case, they crawl through the wire like molasses in January. Very very slowly. That drift rate thingy.

[motion30]

I had some interest in this thread but you two boys knocked it out of me.