where does the power go?

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terri
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Re: where does the power go?

Post by terri » Tue Sep 20, 2005 4:44 pm

Ah, clear. Thank you both!
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Chris Smith
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Re: where does the power go?

Post by Chris Smith » Tue Sep 20, 2005 5:51 pm

Potentials are not work, or work done
Horse power is defined by the Pound/ foot as in torque,
Torque is defined by force times angle, not variable angle times force.<p>
From any first year Physics books.......<p>There are many colloquial meanings for the word “work”. <p>Because of this fact it becomes necessary for a scientists to state “Exactly” what he or she means by the word.<p>The meaning adopted universally in science is as follows:<p>The work [W] is done by a force [F] that acts on an object as the object moves through a small displacement [R]<p>COMPOUND Units for work are as follows: [note the word compound]<p>SI ........newton /meter
cgs.......... Dyne / meter
British ....pound/foot<p>Work has no direction there fore it is a scalar quantity.
************************<p>Definition of Power<p>POWER is defined to be the RATE at which work is being done.<p>That’s work done / time taken<p>Power = Force times velocity<p>Power = force times distance/ time<p>All of these relations are “equivalent”. <p>COMPOUND Unit systems for power are as follows:[note the word compound] <p>SI................ Joule / Second
cgs................erg/ second
British .........pound /foot / second<p>A common unit called the Horse power is used even though it belongs to none of these systems.

One HP is defined as 550 pound/ foot which makes it “EQUIVALENT” to 746 watts.<p>Work is sometimes expressed in terms of a unit called the “kilowatt [times] hour” or KWH.<p>It does not belong to our three basic unit systems and should therefore be used with caution.

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Re: where does the power go?

Post by Deal » Tue Sep 20, 2005 7:21 pm

Laughed at the nutty cranks about conversion units. Lost in the calculations was stone real life observation that the car slows down when Alt kicks in. I know all the alternator calculations because as energy stingy sailor have upgraded to high amp alt and know the math all the way down to the size of the pulleys (or sheaves). What was sidesteped and lost between the foot and the pounds is that energy has a price. Given escalating price of gasoline, we need our smart people in this thread to be turning our attention to urgency of our situation. Your car lights are not free energy wizardry switched by buttons. Every engine sucks calculations of foot pounds and cost in the intake and recalculates in terms of oil. Every facet of our present infrastructure has been built on energy of petroleum. We need our best minds to calculate the consequences of shrinking supply and increased world demand. I hope we can do this thing.

terri
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Re: where does the power go?

Post by terri » Tue Sep 20, 2005 8:02 pm

"...energy has a price."<p>we know that energy has a price and that is why many threads along this line were started in this forum and what we are doing is kicking around the possibilities as well as the impossibilities which are usually promulgated by folks who don't necessarily understand what can and can't be done, even so with the viewpoint of some of us that what we think is impossible now may be possible tomorrow and even though some of us have a sense of humor and some of us have a distorted sense of correctness and get sidetracked on statics versus dynamics and I think if any one of us lived in a wind energy area we'd try to put up our own turbines but others would question how much energy it would take to mine the iron and coal to get the steel for the tower and how long it would take to amortize this cost and all of us know that the ultimate answer to the topic's title "where does the power go?" is that it goes to heat and some of us try to divert more and more of that heat to useful work and some of us have opined that the only real solution is to decrease demand by cutting the population of the world but still others point out that the big companies need an ever-expanding market so they're not for population control and junk 'n whatever.<p>And are you related to James Joyce?<p>[ September 20, 2005: Message edited by: terri ]</p>
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Chris Smith
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Re: where does the power go?

Post by Chris Smith » Tue Sep 20, 2005 9:34 pm

The environment [not oil] can provide all of our energy needs that we can use for the foreseeable future. <p> The only things holding us back here is the small thoughts, large greed, and a lack of imagination.<p> The suns power alone at todays conversions for solar, can produce 85 times the total energy consumption of the US. <p>And the only trade off here besides a national program is that we replace every roof surface in the country with solar panels. <p>But with our current Arab in the white house, and the small minds of Congress, hell will freeze over before any of this ever happens. <p>And after that Ice age comes to hell, the ocean currents will be off limits to power producing engines as well as possibly even the solar proposition

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Re: where does the power go?

Post by rshayes » Tue Sep 20, 2005 10:58 pm

Corn can be used to make alcohol, which can be used as a fuel. It also requires a great deal of care to grow (for example, pesticides).<p>The kudzu vine is an outright nuisance and practically impossible to stop growing, with or without human intervention. It apparently can grow about a foot a day. Commercial growth of the kudzu vine should be very cheap relative to corn.<p>The queation would be whether or not kudzu vine can be either processed into alcohol, some form of diesel fuel, or used directly to fuel powwer plants. Large scale cultivation might also start removing greenhouse gasses and converting them to hydrocarbons, forming a closed cycle, rather than the open cycle which occurs with fossil fuels.

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Chris Smith
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Re: where does the power go?

Post by Chris Smith » Wed Sep 21, 2005 8:02 pm

Will
My exams were in English, almost scottish from my teacher.<p>Yours Im sure were in American.

rshayes
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Re: where does the power go?

Post by rshayes » Thu Sep 22, 2005 12:31 am

The SAT and ACT tests are usually given in English in this country. I don't even know if there is a Gaelic version.<p>[ September 22, 2005: Message edited by: stephen ]</p>

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Re: where does the power go?

Post by terri » Thu Sep 22, 2005 2:54 am

<p>[ September 22, 2005: Message edited by: terri ]</p>
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Chris Smith
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Re: where does the power go?

Post by Chris Smith » Thu Sep 22, 2005 9:57 am

Your SATs are given in American, that much I am certain. And SATs and Degrees are not the same thing. <p>English is reserved for the UK and its colonies. <p>I dont know any SATs in this country that spell these words,..... Tyre, Colour, Aluminium, do you?

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Re: where does the power go?

Post by Newz2000 » Thu Sep 22, 2005 10:48 am

If this conversation is going to continue, can someone please post it under a new topic? I'm sad to see my name associated with this and I'm tired of getting all of the e-mails saying someone replied to my message.<p>If, by chance, we get back onto the subject of the original question (what was it again?) then go ahead and resume posting to this thread, but as for (lbs|foot)*(foot|lbs) and what language was used on standardized tests, please start a new topic.

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Re: where does the power go?

Post by Will » Thu Sep 22, 2005 2:45 pm

Chris (LOL), As part of your continuing English and engineering Units lessons - (i) You use a capital 'S' with Scottish (ii) if you choose to condense 'I am ' into 'I'm' then you have to use the apostrophe as shown.
How much cash do you have to bet that my exams were in American ?
BB

rshayes
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Re: where does the power go?

Post by rshayes » Thu Sep 22, 2005 4:16 pm

Hello Matt,<p>You do deserve a little more coherent answer to your original question, especially after several pages of digression.<p>In an automotive electrical system, the primary source of power is the battery. The voltage in the system depends mostly on the battery state and condition.<p>A lead-acid battery is usually considered to be 2.2 volts per cell. Twelve volt systems use six cells in series, which results in a nominal voltage of 13.2 volts. The voltage of a lead-acid battery depends on its state of charge. A discharged battery will be a little lower in voltage. The battery also has some internal resistance. This is usually very low, but significant.<p>Starting an engine may require several hundred amperes of current. Due to the internal resistance of the battery, the voltage during cranking can drop to the 8 to 10 volt range. On a cold day, it may get even lower.<p>Once the engine is started, the battery needs to be recharged. This is done by maintaining the voltage on the battery terminals at about 14 volts. If the battery has been discharged, its internal voltage will be less than this, and a heavy charging current will flow into the battery, limited by the resistance in the circuit. As the battery charges, the current decreases, and is fairly small when the battery is fully charged.<p>The voltage of a generator depend on two things, the generator speed and the field current. There is some internal resistance, so the generator voltage will also decrease when it is delivering a heavy current. The engine speed is variable and uncontrolled. At low speeds, the generator is usually incapable of putting out 14 volts, even with full field current. As the speed increases, the voltage increases. A relay is used to keep the generator disconnected until its voltage is higher than the battery voltage. When the generator voltage exceeds the battery voltage, the relay connects the generator to the battery and current begins flowing into the battery. As the engine speeds increases further, the battery voltage will rise due to the charging current. When this voltage exceeds 14 volts or so, the voltage regulator begins to reduce the generator field current to keep the battery voltage around 14 volts. As the battery charges, the current decreases, and the voltage requlator reduces the field current still further.<p>The torque required to turn the generator depends on the current being delivered by the generator. The electrical load on the generator is reflected as a mechanical load on the engine. Energy is represented by a force acting through a distance. When the load on a generator is light, it is easy to turn, and the force supplied by the engine is small.<p>If the electrical load on the generator is light, the mechanical load on the engine is reduced and the transfer of mechanical power to the generator is also reduced.<p>The speed of the engine and the field current determine the generator output voltage. The torque required to turn the generator depends on the load current that the generator is delivering. No electrical load, no reflected mechanical load, and no mechanical power taken from the engine.

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Chris Smith
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Re: where does the power go?

Post by Chris Smith » Thu Sep 22, 2005 5:20 pm

No Will, everything in English is optional.
Caps, apostrophe, comma, etc.
And they even vary from continent to continent.
There are no rules stipulating the mandatory use of any of these accessories. <p>Engineering doesn’t have this luxury because when you change one parameter off the standard, you change all the other factors that make up the “compound unit”. <p>Try changing one of the units in this equation and see what happens to the others. <p>E=Mc squared.<p>If E is = to one, and it is = to a mass of one, and the constant doubles from 2 to 4, the E doesn’t double but quadruples, all from a simple change in one part of the equation. <p>Same goes for the Pound V.S. the Foot in the compound unit called a HP.<p>Substitute one for the other and it is no longer equal.

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Re: where does the power go?

Post by Robert Reed » Thu Sep 22, 2005 5:28 pm

Stephan Good post , but I have one minor picking point. That being individual cell voltage is 2.1 volts per cell, Thereby producing 12.6 Volts for a 6 cell battery. I have never seen a fully charged battery in good condition vary from this voltage. 13. 2 volts is a general standard for bench testing mobile electronic equiptment (the mid point between battery voltage and charging voltage). It is also the level usually chosen for long term trickle chargers.

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