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How do you calculate percentage of something?

Amount divided by Something times 100.

75/300x100=25

Simple arithmetic that apparently way over your head.

Fool wrote: ↑Sat Aug 24, 2024 8:01 am How do you calculate percentage of something?

Amount divided by Something times 100.

75/300x100=25

Simple arithmetic that apparently way over your head.

300 is 80% of 375

What then is the remainder?

You are not using the proper scale for the circumstance.

The scale is 0 to T-hot

T hot in this case was 375 not 300.

It isn't 75/300 it's 75/375

As per the "Carnot efficiency limit" formula.

There is nothing wrong with your math in some other context. In the context of how "Carnot efficiency" is calculated it's wrong.

(Th-Tc)/Th x 100%

(375-300)/375 x 100%

75/375 x 100%

That's 75/T-hot, not 75/T-cold

0.20 x 100% = 20%

Do you wish to change the rules for how "Carnot efficiency" is calculated?

That would be just one more inconsistency to add the the general confusion surrounding the 2nd so-called "Law" and the so-called "Carnot efficiency limit".

Tom Booth wrote:Starting at, for example, 300°K ambient

Raising T-hot to 375°K is an increase of 20%

375 is 20% higher than 300.

Starting at 300 rising to 375 is 25% higher. As properly said.

Starting at Tc of 300, for a Carnot efficiency of 20%, Th will be 375.

Your problem is understanding percentages. Not calculating numbers in an equation, that anyone can do. Terms for standard equations, and how they are set up are the first thing that must be done correctly if you expect anyone to trust your mathematics. Denying that you are wrong is the best way to be written off.

It is a slippery slow. Start out wrong, people will just figure the rest will have more errors and lose interest as I have.

Fool wrote: ↑Sat Aug 24, 2024 12:24 pm

Tom Booth wrote:Starting at, for example, 300°K ambient

Raising T-hot to 375°K is an increase of 20%

375 is 20% higher than 300.

Starting at 300 rising to 375 is 25% higher. As properly said.

Not really.

Starting at 300 rising to 400 is 25% higher in terms of the final height. Obviously.

I did not say "20% higher in terms of the starting temperature T-cold" because that is not how Carnot efficiency is calculated. It is calculated in terms of T-hot from absolute zero.

Yes, if you figure on the basis of T-cold, then you would be correct, but that is not what I said, that was your own erroneous assumption or misinterpretation of what I said.

If you climb to the top of a 375 foot high hilltop, when you reach 300 feet you've climbed 80% of the way up. At 375 feet you've climbed the remaining 20%.

There is nothing "wrong" in that.

To calculate the percentages based on some arbitrary midway point rather than the total height is nonsensical.

Starting at Tc of 300, for a Carnot efficiency of 20%, Th will be 375.

Your problem is understanding percentages. Not calculating numbers in an equation, that anyone can do. Terms for standard equations, and how they are set up are the first thing that must be done correctly if you expect anyone to trust your mathematics. Denying that you are wrong is the best way to be written off.

It is a slippery slow. Start out wrong, people will just figure the rest will have more errors and lose interest as I have.

Fool wrote: ↑Sat Aug 24, 2024 12:24 pm

Your problem is understanding percentages. ...

I think that's YOUR problem.

A percentage, in the REAL world applies to some thing that some part of that thing is the percentage of. Like the temperature scale between 0°K and 375°K is the "thing".

Context matters and purpose matters, what do you want to know?

Take a shipment of part feather pillows and part dumbbells.

What percentage of the shipment is pillows and what percentage is dumbbells?

Do you want that in terms of weight or volume?

Do you want to know because the weight capacity of the truck is limited or because space on the truck is limited? Or some other reason.

Context matters and determines, the method of calculation and the result.

It takes some common sense, which you obviously lack

I'd admit I was wrong, if I thought I was wrong. I'll admit percentage can be calculated differently and produce different answers depending on the context and the application.

One way is not any more wrong or right unless you do as you are doing and apply a method that does not fit the application.

The application we have been discussing here is the Carnot Limit and the method of calculating percentage you are using is not applicable.

Your a moron.

You're a moron. LOL Learn to spell too.

Usually I don't pick on a person's spelling because I make enough of my own and typos. But adding name calling just left it wide open. There are four fingers pointing back at you. Mellow out and have another lude, dude.

You see Tom, making the statement that 375 is 20% higher than 300, is wrong.

If you meant to say, the Carnot efficiency for 300 to 375 is twenty percent, you should have said it that way.

By your error, you seemed to be hinting that Carnot is wrong because a 25% increase leads to only a 20% efficiency gain. The rest was too confusing to be meaningful.

Anyone, 6th grade and on, can plug numbers into a given equation. I requires higher education to describe it correctly. And understand why.

When you say percent, you have to define what it is a percent of. You defined it as 300. Now you are flip flopping around trying to correct you error by saying we should always use the higher value even when you say, starting at. That is just wrong.

.

Fool wrote: ↑Sun Aug 25, 2024 11:57 am ...
When you say percent, you have to define what it is a percent of.

Right. In this case, that should be obvious given the context.

You defined it as 300.

No I didn't.

You did, moron.

Now you are flip flopping around trying to correct you error by saying we should always use the higher value even when you say, starting at. That is just wrong.

I did not say "always" anything. Above I say "Starting at 300 rising to 400 is 25% higher in terms of the final height".

That should be obvious given the context.

I'm not "flip flopping". You're just some kind of lunatic who takes every word literally regardless of context. Or you think your own error in judgement is someone else's mistake.

In discussing Carnot efficiency the ∆T is taken as a percentage of the absolute temperature scale between 0°K and T-hot.

Presumably, posing as an expert on the subject, you should already know that.

You can believe whatever you like, but on a scale between 0°K and 375°K regardless if you start at 300° and go up or start at 375° and go down, or just look at the whole, the 75° ∆T is 20%

Saying it is 25% is wrong. 75 is 25% of 300 which is on a scale of 0° to 300°

As soon as you reach 375 the ∆T becomes 20% of the whole.

Starting at 300° and ending at 375° you've gone up 20% of the whole. That's obvious to anyone with two brain cells.

However you look at it, or wherever you start, going up from 300 or down from 375:

75 is 20% of 375.

Your method of calculating percentage in this case is inapplicable and illogical.

Tom Booth wrote:As soon as you reach 375 the ∆T becomes 20% of the whole.

Yes 75 is still 20% of 375. And it is still 25% of 300. Its your terminology that is in error.

Tom Booth wrote:375 is 20% higher than 300.

Wrong. 375 is 25% higher than 300. Correct.


It makes little sense the way you wrote it.
.

Fool wrote: ↑Mon Aug 26, 2024 12:13 am

Tom Booth wrote:As soon as you reach 375 the ∆T becomes 20% of the whole.

Yes 75 is still 20% of 375. And it is still 25% of 300. Its your terminology that is in error.

Tom Booth wrote:375 is 20% higher than 300.

Wrong. 375 is 25% higher than 300. Correct.


It makes little sense the way you wrote it.
.

It makes perfect sense in the context.

I don't really know in what context it would make sense to calculate one part of some whole in terms of a percentage of some other part.

But I'm not at all surprised that makes sense to you.

I drove 300 miles, then another 75.

The last part of the journey is 20% of the trip.

You would say that the last part of the journey is 25% of the first part of the trip.

What useful information does that convey?

Or suppose you travel 100 miles total

First 20, then 80.

the first part was 20%

Then the second part is 400%?

So if I go 20 miles and stop, then go another 80 miles, by your method the second part of the trip is 400% ?

In what context does this make sense?

This exercise in logic illustrates the problem with Carnot efficiency, as it so happens.

If you add 75 joules to the engine bringing the temperature up from 300 to 375 and the engine converts 75 joules to work, Carnot efficiency calculates that the engine has only converted 20% of the heat and 80% goes to "waste heat".

As a matter of abstract mathematics with no correspondence to physical reality the math is "correct".

But in the context of real engines in the real physical world if you add 75 joules and convert 75 joules to work, the actual efficiency is 100% with zero physically measurable waste heat.

Though apparently you would like that to be changed to 25% efficiency?

Three people run a 100 meter race, however John ran 90% , Alice ran 100%, and Tina ran 20% further for 120 meters.

John 90 meters.
Alice 100 meters.
John 120 meters.

You only go back a use John's distance if you want to. Then you redefine the percentages from 120. John ran 90/120•100=75% of Tina's run. Etc...

300 is twenty percent lower than 375. Correct. When you say it that way, your starting point is 300.

375 is not 20% higher than 300, it is 25% higher.

If you want to use the final point you need to say 300 is 80% of 375 for a twenty percent difference. Or 300 is 20% lower than 375. You need to define your percentage base correctly. You didn't. You defined it as 300.

If you have a bank account of $300 your banker is not going to give you $75 for 20% interest. He's going to give you $60. He will add 20%. $360 will be 20% higher than the starting amount of $300 . $375 is some fantasy you concocted.

If I put 20 Watts Work into a heat pump, and 80 Watts heat is put out to the hot zone, AKA house, that is a COP of 4 or 400%. Any more questions?

Percentage is based on a given. You gave 300. 300 was what you started with. 20% of 300 is 60. 20% higher than 300 is 360. 300+60=360.

The whole concept of percentage IMO is lame. I prefer factors. 80 is greater than 20 by a factor of 4 . Multiplying factors by 100, is just adding confusion. However we are stuck with those political conventions of percentage. It's wise to learn them correctly. 100% is just a factor of 1.0 .

A factor of 1.25 for 300 gives 375. 300•1.25=375 . 375 is grater than 100 by a factor of 1.25 .

Or 375 is greater than 1.25 by a factor of 300. Think base first, then, factor of that base.

The Carnot limit is just a factor until some jackass multiplies it by 100 for little apparent reason. We could just have easily made it the number 10 or 1000, etc...

20% more is a factor of 1.20 ; 300•1.20=360 .
375 never happens.

Working backwards is wrong 375 does not equal 1.20•300 .

.

Tom Booth wrote:But in the context of real engines in the real physical world if you add 75 joules and convert 75 joules to work, the actual efficiency is 100% with zero physically measurable waste heat.

Good luck with that. How did you measure waste heat? How much input heat? How much Work out? What is your experimental errors? You will need to supply a calibrated indicator diagram, and or a work output, measurement. To prove any of that fantasy. Your temperature measurement, that is equal to room temperature, has only proven that the heat sink is still working.

Fool wrote: ↑Mon Aug 26, 2024 7:48 am Three people run a 100 meter race, however John ran 90% , Alice ran 100%, and Tina ran 20% further for 120 meters.

John 90 meters.
Alice 100 meters.
John 120 meters.

You only go back a use John's distance if you want to. Then you redefine the percentages from 120. John ran 90/120•100=75% of Tina's run. Etc...

300 is twenty percent lower than 375. Correct. When you say it that way, your starting point is 300.

375 is not 20% higher than 300, it is 25% higher.

If you want to use the final point you need to say 300 is 80% of 375 for a twenty percent difference. Or 300 is 20% lower than 375. You need to define your percentage base correctly. You didn't. You defined it as 300.

I'll admit I did not define the percentage base. I think that is obvious given the context.

I did not however explicitly define it as 300. That was your interpretation and certainly not my intent and not deducible merely from the words: "375 is 20% higher than 300".

The intent is self evident unless you have a "make wrong" fixation

If you have a bank account of $300 your banker is not going to give you $75 for 20% interest. He's going to give you $60. He will add 20%. $360 will be 20% higher than the starting amount of $300 . $375 is some fantasy you concocted.

If I put 20 Watts Work into a heat pump, and 80 Watts heat is put out to the hot zone, AKA house, that is a COP of 4 or 400%. Any more questions?

Percentage is based on a given. You gave 300. 300 was what you started with. 20% of 300 is 60. 20% higher than 300 is 360. 300+60=360.

The whole concept of percentage IMO is lame. I prefer factors. 80 is greater than 20 by a factor of 4 . Multiplying factors by 100, is just adding confusion. However we are stuck with those political conventions of percentage. It's wise to learn them correctly. 100% is just a factor of 1.0 .

A factor of 1.25 for 300 gives 375. 300•1.25=375 . 375 is grater than 100 by a factor of 1.25 .

Or 375 is greater than 1.25 by a factor of 300. Think base first, then, factor of that base.

The Carnot limit is just a factor until some jackass multiplies it by 100 for little apparent reason. We could just have easily made it the number 10 or 1000, etc...

20% more is a factor of 1.20 ; 300•1.20=360 .
375 never happens.

Working backwards is wrong 375 does not equal 1.20•300 .

.

What I think everybody can be very certain about is whatever way I expressed the percentage, you would have said it was wrong and proceeded to argue the opposite, as is your inclination; to make an argument out of any triviality.