Sometimes, it just hits you

[Mark Hammer]

So my son asks me for some help with his grade 8 science homework because there is one question he's stuck on.  "How does balancing the wheels on a car affect performance?"

As I'm explaining to him about how balancing wheels helps to maintain equivalent road contact on all four wheels at all points in rotation, it suddenly occurs to me: that's why we match JFETs in phasers.

Funny how those analogies just leap out at you sometimes.

[jacobyjd]

Makes me wonder what kind of mpg I'm getting out of my phase 45...

[composition4]

Sometimes, it just hits you - Mark Hammer

Sorry couldn't resist, I actually laughed out loud when I saw that. You're probably over it after x years of the name

Jonathan

[ayayay!]

Thanks for sharing that Mark!  Last night, my 1st grader was doing his homework.  He had to draw 3 pictures for his vocabulary words:  Equal, Talent, and Believe.

Equal wasn't too bad.

Talent was trickier.

But Believe?  How do you draw a picture of that? 

I told him about the wind, and how you can't see it but you know it's there.  He didn't get it.  So he thought for a moment and said, "I believe in Mom"  and proceeded to draw a picture of he and my wife holding hands.

That's-a my Boy!!!!!   

[Mark Hammer]

That was sweet...really.

Between the ages of 5 and 15 and 25, it can sometimes be "I don't know what happened.  It worked before I boxed it up."

In any event, before we get moved to OT, the intent was not to start a thread on parenting or homework, but rather just to say that sometimes you stumble across analogies completely outside the electronics domain that make things within the electronics domain that much clearer.

[frank_p]

http://www.ece.utah.edu/~ece3510/Notes_Mech_to_Elect.pdf
http://www.ece.utah.edu/~ece3510/Notes_Mech_to_Elect_Expls.pdf
Go to Lectures and notes:
http://www.ece.utah.edu/~ece3510/ECE3510hw_S10.htm

http://www.ece.utah.edu/~ece3510/Notes_PhasorEx_F05.pdf

Those things can hit you for a long time.

[jkokura]

At least you weren't hit by a 1790. Nothing can stop that.

Jacob

[Joe Viau]

The designer of this keyboard, John Karidis, was inspired by his 3-year-old daughter playing with building blocks:

http://en.wikipedia.org/wiki/IBM_ThinkPad_Butterfly_keyboard

[jdub]

...sometimes you stumble across analogies completely outside the electronics domain that make things within the electronics domain that much clearer.

I agree wholeheartedly.  In the realms of cognitive theory, there are those who would suggest that such cross-mapping of metaphors (analogical thinking) forms the basis of learning, even that language and possibly consciousness itself are based on metaphor (corresponding in physical terms to neural firing patterns in the brain, which may be similar for different concepts).  In electronics, one has the whole "water as current" metaphor which goes a long way toward helping people understand basic concepts, for example.

And it is a very neat feeling when those analogies- in whatever field you might be into- strike home.  This has happened to me in my understanding of music many times, as it probably has for all of us...

[Joe Kramer]

Actually a great idea for a thread, since sharing mental pictures can help illuminate difficult concepts, at least for dim brains like mine. . . . 

Here's one that hit me.  I was re-stringing a guitar, tightening and tightening the string, thinking about how that tension is a form of stored energy.  Each time you pluck that tightened string, you release the stored energy.  Then it suddenly hit me: that's sort of how a transistor works. The proper DC bias across the collector and emitter is like a guitar string under tension, and sending a signal to the base sort of "plucks the string."   . . . Anyway, worked for me!

     

[ayayay!]

Okay, I've got one:  I think of a Transistor as an engine, with the hfe representing horsepower.  You wouldn't put a 500 HP modified HEMI on a lawnmower, but it would be fine in that Charger.  But for that mower, the 5HP Briggs & Stratton would be perfect! 

Kinda like a MPSA18 being over the top for a silicon FuzzFace, but a 2n2222 being just right. 

Loose analogy but you get the point. 

[frank_p]

Here's one that hit me.  I was re-stringing a guitar, tightening and tightening the string, thinking about how that tension is a form of stored energy.  Each time you pluck that tightened string, you release the stored energy.  Then it suddenly hit me: that's sort of how a transistor works. The proper DC bias across the collector and emitter is like a guitar string under tension, and sending a signal to the base sort of "plucks the string."   . . . Anyway, worked for me!

A string is a continuation of mass and elasticity.

Mass-> Capacitance
Spring constant -> Inductance
Resistor-> Friction

So the string is more like a LC filter tuning a frequency.

Plucking of the string is injection of energy in the system.  The oscillation occurs when quantities of energies will be exchanged back and forth from cinetic to to potential.  The string will stop vibrating when that energy will be dissipated trough internal friction of the material and in air.  This is damping and the electrical equivalent is the resistor.

[Joe Kramer]

A string is a continuation of mass and elasticity.

Mass-> Capacitance
Spring constant -> Inductance
Resistor-> Friction

So the string is more like a LC filter tuning a frequency.

Plucking of the string is injection of energy in the system.  The oscillation occurs when quantities of energies will be exchanged back and forth from cinetic to to potential.  The string will stop vibrating when that energy will be dissipated trough internal friction of the material and in air.  This is damping and the electrical equivalent is the resistor.

Interesting Frank, and thank you.  But you'll notice that in both my analogy and your physics comparison, nothing at all will happen unless the string is under tension.  For me, it's still useful to think of that tension as stored energy.  (A similar analogy is the surface tension that exists between a body of water and atmospheric pressure, and what happens when that tension is disturbed).  At any rate, the whole beauty of metaphors is that, while there may be an "apt" one, there is no "correct" one.  If they don't help for you, you're free to ignore them without any detriment, and to imagine something that does help you to better understanding.



 
PS: An thought-provoking book on the whole subject is "Metaphors We Live By," by George Lakoff and Mark Johnson.  The premise being that all language and thinking is essentially metaphorical in nature. . . .

[frank_p]

Interesting Frank, and thank you.  But you'll notice that in both my analogy and your physics comparison, nothing at all will happen unless the string is under tension  .  
For me, it's still useful to think of that tension as stored energy.  (A similar analogy is the surface tension that exists between a body of water and atmospheric pressure, and what happens when that tension is disturbed).

Completely right. without tension there is no stored energy, or potential energy.  A Voltage is a potential energy: that is an energy ready to do a work.  The problem of the string is that all the portions of the string have a mass and an elasticity constant.  The tension that you put by pulling with the string with the tuner and with your finger is not in the same direction.  If you take just a point on the middle of the string under tension but at rest, the tension is there but only horizontally.

If from there you pull with your finger at the middle of the string, the point is  pulled upwards by your finger.  But since that will deform the string (the shape of a house roof), the string tension will increase and change direction.  Part of the string tension will want to pull the middle point, down.

When you leave your finger off of the string, the work that had been done to put more tension will pull and accelerate the middle point down.  The tension (potential energy) is then converted into kinetically energy and the maximum speed of the middle point will be when the string will be at it's flat or straight position again.

But inertia want to continue with the same speed and the same direction.  So the middle point will go down, under the straight string position but will loose it's cinetic energy (speed) because the tension will rebuild in the string (potential energy growing).  This will continue until the middle point will go to rest at the lowest position.  

And the game will start over in the other direction.
Etc...  : this is how the tension of the string is acting on a point along the string so it can act as a force that is perpendicular to its initial position !

This will go on at a given frequency and will behave like an inductor-capacitor oscillator, not like a transistor.

 At any rate, the whole beauty of metaphors is that, while there may be a "apt" one, there is no "correct" one.  If they don't help for you, you're free to ignore them without any detriment, and to imagine something that does help you to better understanding.

Yes and no...
The important point to underline here is that this is not only metaphors and analogies.  When you take time and care to analyse both mechanical and electronics topologies, in some and many instances they can be modelled by the same maths and they will behave alike.  You can build all kind of vibration filters with springs, dampeners and masses just like you would build electrical frequency filters with coils, resistors and caps.

[Joe Kramer]

. . . this is how the tension of the string is acting on a point along the string so it can act as a force that is perpendicular to its initial position !

This will go on at a given frequency and will behave like an inductor-capacitor oscillator, not like a transistor.

Thank you again, Frank, your explanation is very clear.  However, I'm afraid you are missing my point.  My analogy is not a comparison between two material objects which may or may not behave according to similar principles of physics.  No doubt many things do behave similarly to each other according to physics, and as far as that goes, again, your explanation is clear and well said.  My main idea lies not in how a string is a physical counterpart of a transistor, but in the rather non-material idea of stored energy or Potential, as such.  That idea can be seen all around us: the surface tension of water, a battery, a seed, DC across the nodes of a transistor, a taut guitar string.  Under the right circumstances, that stored energy is released: the water ripples, the electrons course, the seed sprouts, the transistor amplifies, the string sounds.  Call my thinking poetic, and I won't be insulted at all, because I agree.  If you don't see any likeness among these things, it's okay, there are as many ways to look at a thing as there are eyes.

FWIW, I think we are talking at cross-purposes, and here's why: Let's say that, whenever I think of England, I think of Big Ben.  I'm not saying "England is Big Ben" in a literal sense, but in a figurative one.  Something rather non-material in the idea of Big Ben epitomizes and helps me grasp the greater whole of all that's entailed in the history, culture, and so forth of England.  In that sense, Big Ben is "like" England to me.  By the same token, I think what you are trying to do is explain to me that, since there is nothing resembling the Thames River or Piccadilly Circus in the structural make-up of the clock tower, therefore Big Ben is not "like" England, but much more like a pocketwatch or a musicbox.

Maybe for the sake of variety, we could shift the discussion to the OP's comparison of car tires and transistors. . . .

 

[Ronsonic]

Check the great one, Harry F. Olson's book on Dynamic Analogs. He takes this dog all the way around the block.

[jdub]

My analogy is not a comparison between two material objects which may or may not behave according to similar principles of physics.

+1.  I think Joe's observation of the metaphorical connection between disparate objects is correct, and forms the basis of "poetic thought", but Frank's pointing out the limitations is also appropriate. Metaphors always break down when subjected to intense rational scrutiny, since there can never be a complete one-to-one correspondence betwen two concepts or things- if there were, the two would be identical.  Metaphor appears to be a similarity in pattern, so to speak, and as such needs to be apprehended in a different way than bit-by-bit breakdown.  I tend to think of it in terms of motif or variation in music: a variation possesses the same general melodic contour as the original melody but need not contain the same notes; nontheless it is recognizable as an echo of the original, but in a note-for-note comparison is certainly not identical.  Analogies or metaphors therefore are necessarily limited in terms of left-brain analysis, but can be extremely useful in a right-brain way, prodding the mind to go in a certain direction with it's thinking...

OK, this is way off-topic now...leave it to Mark to get everybody thinking...

[GP]

many ways to look at a thing as there are eyes.

FWIW, I think we are talking at cross-purposes, and here's why: Let's say that, whenever I think of England, I think of Big Ben.  I'm not saying "England is Big Ben" in a literal sense, but in a figurative one.  Something rather non-material in the idea of Big Ben epitomizes and helps me grasp the greater whole of all that's entailed in the history, culture, and so forth of England.  In that sense, Big Ben is "like" England to me.  By the same token, I think what you are trying to do is explain to me that, since there is nothing resembling the Thames River or Piccadilly Circus in the structural make-up of the clock tower, therefore Big Ben is not "like" England, but much more like a pocketwatch or a musicbox.

Not to hijack the thread and send it off topic but i find that quite fascinating. The current buildings of the Palace of Westminster are younger than the foundation of the United States so it seems odd to me that these embody the "history" of England. Coincidentally, as often misinterpreted, "Big Ben" is actually the name of the bell and not the bell tower that houses it. Of course, everyone now refers to it as such but, strictly speaking, the bell tower is simply the bell tower and nothing more. Also, one should take care to suggest that the Palace of Westminster embodies anything to do with the history, culture, whatever of "England" since these buildings were built to house the parliament of the United Kingdom of Great Britain and Northern Ireland, of which England is only a part.