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From: Frank Krygowski <frkrygow@sbcglobal.net>
Newsgroups: rec.bicycles.tech
Subject: Re: Suspension losses
Date: Thu, 16 Jan 2025 12:18:54 -0500
Organization: A noiseless patient Spider
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On 1/16/2025 7:14 AM, zen cycle wrote:
> On 1/15/2025 6:39 PM, Frank Krygowski wrote:
>> 
>> You should look at the energy used for the controls and think about 
>> what becomes of it. Do that in microcopic detail.
> 
> If you think it all ends up as heat (IR spectrum) you have a gross 
> misunderstanding of electronics. First off, the indicators dissipate 
> energy in the visible light spectrum (this is why LEDs are more 
> efficient lighting than incandescent, very little energy is used in the 
> IR spectrum). 

OK, a thought experiment: Take an adiabatic container - that is, a 
_perfectly_ insulated box (a physical impossibility, but useful for our 
analysis). Let the box contain whatever you like - just air, some solid 
objects, whatever.

Cut an LED sized hole in it and insert an LED of your choice so it 
shines into the box. Turn on the LED.

What happens to the light entering the box? Obviously, you don't end up 
with a box full of light, so it isn't stored; it somehow goes away. And 
what happens to the temperature inside the box, and why?

Answer: The temperature of whatever's inside the box will rise. The 
energy put into _all_ spectra by the LED, including the visible light 
spectrum, ultimately converts to heat.

> Secondly, think about your premise that it all turns into 
> heat - this means no energy is available to do any other form of work.
In physics or mechanical engineering, work is defined as force moving 
through a distance, or torque moving though an angle of rotation. Valid 
units of measurement are the same as the units for energy: foot*pounds, 
Newton*meters or Joules, etc. all of which (interestingly) can be 
converted to BTUs, which are normally units measuring heat.

And in general, you're right, energy converted to heat is not normally 
available to do work.

There are exceptions, of course. A device that produces work from heat 
is known as an "engine."

I bought one of these a while ago, as a geek toy. (I used to have a 
larger one as a demonstrator used in Thermodynamics class.)

https://www.amazon.com/gp/product/B0BL29ZF17/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

It's a small Stirling Engine driven by the temperature difference 
between the hot bottom plate and the colder top plate. It sits on top of 
a cup of hot water. Heat flows into the disk on the bottom and flows out 
the top one. I've gotten about 850 rpm out of mine, more if I place an 
ice cube on the top plate.

So an engine is a device that converts heat to mechanical work. But no 
engine can covert heat to work with 100% efficiency.

All of this discussion is stuff normally covered under the topic 
"Thermodynamics."

-- 
- Frank Krygowski