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eHam Forums => Misc => Topic started by: N3DF on May 09, 2013, 11:26:18 AM



Title: Ohm's Law
Post by: N3DF on May 09, 2013, 11:26:18 AM
When I learned Ohm's Law (around 1961), it was E=IR.  Now it's V=IR.  When did that happen?


Title: RE: Ohm's Law
Post by: K1WJ on May 09, 2013, 11:59:12 AM
Last I knew it was still E=IR, V for voltage - no big deal, still calculates the same. 73 K1WJ David


Title: RE: Ohm's Law
Post by: KE3WD on May 09, 2013, 02:47:11 PM
When I learned Ohm's Law (around 1961), it was E=IR.  Now it's V=IR.  When did that happen?

V = Volts = E = Electromotive Force

The I stands for Intensity, BTW.

As to why we are starting to see more use of the V, and even the C, instead of the E and the I, we are, after all, using a living language. 

73


Title: RE: Ohm's Law
Post by: KD0REQ on May 09, 2013, 02:59:14 PM
one more old grump, I guess, who thinks that V instead of E is violating Ohm's Law.  I believe the penalty is I ^2 L


Title: RE: Ohm's Law
Post by: AA4PB on May 09, 2013, 03:07:52 PM
It seems to me that if you are going to use "V" for volts then you should also use "A" for amps and "O" for ohms since they all represent units. So, V = AO  :o

Or, we could just stick with E, I, and R as originally specified since they all represent the things we are measuring rather than the units of measure.


Title: RE: Ohm's Law
Post by: K7KBN on May 09, 2013, 03:59:43 PM
E = IR

E = MC²

Therefore, IR = MC².   ;D


Title: RE: Ohm's Law
Post by: K8AXW on May 09, 2013, 05:36:49 PM
I wish you guys would knock off this line of discussion.  Some @#%&$#% idiot will want his 15 minutes of fame by talking the power-to-be into making this change..... like the idiot that managed to get cycles changed to hertz. 


Title: RE: Ohm's Law
Post by: WB2EOD on May 09, 2013, 06:29:52 PM
Twinkle, twinkle little star
E is equal to IR

Up above the world so high
P is equal to EI

Most important, Murphy's Law supersedes Ohm's Law, Newton's Laws of motion and Cole's Law (shredded cabbage, carrots mayonnaise)

73
WB2EOD


Title: RE: Ohm's Law
Post by: KE3WD on May 10, 2013, 05:05:38 AM

Most important, Murphy's Law supersedes Ohm's Law, Newton's Laws of motion and Cole's Law (shredded cabbage, carrots mayonnaise)

73
WB2EOD

You left out the all-important V.

For Vinegar. 


73


Title: RE: Ohm's Law
Post by: KK4PFQ on May 10, 2013, 03:22:43 PM
..... like the idiot that managed to get cycles changed to hertz. 

I'm still haven't recovered from that one...

73
KK4PFQ


Title: RE: Ohm's Law
Post by: N6AJR on May 10, 2013, 03:49:32 PM
yup 100 motorcycles sounds better than 100 motorhurts.


Title: RE: Ohm's Law
Post by: N4NLQ on May 11, 2013, 09:11:18 AM
How about the change from condenser to capacitor?  Since that changed the component from something that condenses a vapor to a liquid, to something that stores a liquid, shouldn't we have changed "Farads" to "quarts"?


Title: RE: Ohm's Law
Post by: K0OD on May 11, 2013, 01:19:34 PM
Quote
"like the idiot that managed to get cycles changed to hertzt managed to get cycles changed to hertz"

"That idiot" was an international conference in 1930!

One could argue Hertz was the first ham! As has been discussed on Eham,  the VERY appropriate use of Prof Heinrich Hertz's name was delayed mostly by WW2. The German's used "Hertz" rather than "cycles" long before we did.

Wikipedia: "The name was established by the International Electrotechnical Commission (IEC) in 1930.[6] It was adopted by the General Conference on Weights and Measures (CGPM) (Conférence générale des poids et mesures) in 1960, replacing the previous name for the unit, cycles per second (cps), along with its related multiples, primarily kilocycles per second (kc/s) and megacycles per second (Mc/s), and occasionally kilomegacycles per second (kMc/s). The term cycles per second was largely replaced by hertz by the 1970s."

I believe that most of the other radio/electronics SI's have also had multiple names over the decades.


Title: RE: Ohm's Law
Post by: G3RZP on May 11, 2013, 01:28:45 PM
Isn't 'Ohm's law' government housing policy?


Title: RE: Ohm's Law
Post by: KC9TNH on May 11, 2013, 07:44:40 PM
I teach Ohm's Law as E=IR and that is what is on my Ohm's Law "T" Shirt so, no reason to change in my humble opinion. 
The important thing is that the shirt is changed; periodically anyway.
 ;D


Title: RE: Ohm's Law
Post by: K1CJS on May 11, 2013, 07:56:49 PM
Didn't know Ohm practiced Law. :)


Title: RE: Ohm's Law
Post by: W1JKA on May 12, 2013, 05:40:20 AM
Re:K1CJS

Of course he did and a very Calculating lawyer at that,so much so that he was appointed a Circuit Judge.


Title: RE: Ohm's Law
Post by: K1CJS on May 12, 2013, 07:43:26 AM
 ;D


Title: RE: Ohm's Law
Post by: KD0REQ on May 12, 2013, 07:01:31 PM
E = IR

E = MC²

Therefore, IR = MC².   ;D

must be why my projects have too high a blown-the-hay-up ratio.


Title: RE: Ohm's Law
Post by: AC4RD on May 13, 2013, 04:15:27 AM
Having E change to V is a vowel movement.


Title: RE: Ohm's Law
Post by: W1JKA on May 13, 2013, 08:24:11 AM
Re:AC4RD

Eeeeww that stinks  ;D


Title: RE: Ohm's Law
Post by: AA4PB on May 13, 2013, 08:49:48 AM
..... like the idiot that managed to get cycles changed to hertz. 

Actually the change was from "cycles per second" to "Hertz", which made more sense than "E" to "V". It was also done to honor Mr. Hertz.


Title: RE: Ohm's Law
Post by: K8AXW on May 13, 2013, 09:12:52 AM
I've often wondered why they couldn't have picked some other way to "honor Mr. Hertz" instead of such a disruptive.....no.... stupid.....no... the correct word doesn't come to me now.

Everyone knows what a "cycle" is.  What the hell is a hertz?   ::)


Title: RE: Ohm's Law
Post by: AC4RD on May 13, 2013, 09:16:06 AM
Everyone knows what a "cycle" is.  What the hell is a hertz?   ::)

It's the same thing as a henway.   ;)



Title: RE: Ohm's Law
Post by: K0OD on May 13, 2013, 09:46:10 AM
Cycles (or, yes, cycles per second), makes sense to English speakers that utterly dominated the literature back then. My ee son is amused when I often refer to kilocycles and megacycles. But "hertz" is as good as cycles for most of the world nowadays.

It's too late I know, but I prefer that they should have used "hertz" as a the unit for voltage. As in, "Damn that HV hertz!"

We'd probably have fewer electrocutions if signs read: "Danger High Hertz!"


Title: RE: Ohm's Law
Post by: AA4PB on May 13, 2013, 10:08:58 AM
Everyone knows what a "cycle" is.  What the hell is a hertz?   ::)

That's exactly the problem. People used "cycle" as though it was a measure of frequency. In fact, it is not and never has been. The measure of frequency was "cycles per second". The change to Hertz (meaning cycles per second) was a way to counter that. Yes, it took some getting used to  ;)



Title: RE: Ohm's Law
Post by: W0DV on May 13, 2013, 05:34:31 PM
I teach Ohm's Law as E=IR and that is what is on my Ohm's Law "T" Shirt so, no reason to change in my humble opinion. 

"Change" - didn't some politician try to foist that on the American People?  How's that working out?

A "T" shirt eh? I want one of those. Thats the way I learned ohm's law also, back in 1982 when I was in electronics school. E= Potential Difference,  I= Electron Flow, R=Resistance, P=Power. 1st day of school, pretty basic stuff.


Title: RE: Ohm's Law
Post by: WB6DGN on May 17, 2013, 12:10:15 AM
Quote
E= Potential Difference

The 'E' stands for 'Electromotive Force" which also got bas******** to "voltage" and, then, of course, someone attempted to change the 'E' to a 'V'.
If somebody thinks they need to honor all these guys, BUY 'EM A BEER, next time you see 'em in the bar, but leave the self-explanatory symbols and terms alone!
Tom


Title: RE: Ohm's Law
Post by: W0DV on May 18, 2013, 02:35:09 PM
Quote
E= Potential Difference

The 'E' stands for 'Electromotive Force" which also got bas******** to "voltage" and, then, of course, someone attempted to change the 'E' to a 'V'.
If somebody thinks they need to honor all these guys, BUY 'EM A BEER, next time you see 'em in the bar, but leave the self-explanatory symbols and terms alone!
Tom

I'm sure you are correct. However, when I went to college in the early 80's, voltage was described to us as "potential difference", and that terminology was used frequently with Ohms Law, and in physics class. Current flow cannot take place unless there is a path for electron flow from one "potential" to another. The vernacular, and terminology used in Physics stuck with me.


Title: RE: Ohm's Law
Post by: KA4NMA on May 18, 2013, 05:24:46 PM
I learned ohms law by Lake Eire -  E=IR=E; Lake Eire.
I know this is a misspelling, but it helped me over 30 years ago.

The resister color code was taught to me by my brother - Big Boys rape our girls, but Violet gives willing.   Yeah I know it is bad....

Randy ka4ma


Title: RE: Ohm's Law
Post by: AA4PB on May 18, 2013, 05:29:34 PM
E = "Electromotive force" which = "difference of potential" which is measured in "Volts".  ;)



Title: RE: Ohm's Law
Post by: K8AXW on May 18, 2013, 09:27:37 PM
Randy:  That's the way I learned it too but also learned one for mixed company:

Bad Boys Ruin Our Grass But Violets Grow Wild.

Al - K8AXW


Title: RE: Ohm's Law
Post by: KE3WD on May 19, 2013, 06:29:57 AM
Both of ya give the PC version from the way we learned it back in the fifities...


*grin*


It may have been UN P.C. -- but darn near every class member *remembered* the mnemonic from the first time it was heard! 

And, at that time, I was the only black member of the class. 

So what?  The class was about Electronics, not social engineering...



73


Title: RE: Ohm's Law
Post by: WB2EOD on May 19, 2013, 12:56:24 PM

better be right or your great big venture goes wrong


Title: RE: Ohm's Law
Post by: W0DV on May 19, 2013, 08:27:01 PM
E = "Electromotive force" which = "difference of potential" which is measured in "Volts".  ;)



An intelligent, thoughtful answer!

Thank You,

Dave


Title: RE: Ohm's Law
Post by: WB6DGN on May 22, 2013, 10:13:52 PM
Randy:  That's the way I learned it too but also learned one for mixed company:
Bad Boys Ruin Our Grass But Violets Grow Wild.
Al - K8AXW

You forgot "yellow".  You'd need to make it "bad boys ruin our young grass....." or yellow grass or ??

Tom


Title: RE: Ohm's Law
Post by: KE3WD on May 23, 2013, 06:46:43 AM

Way back in school, in the early 60's, they were still teaching the old politically incorrect mnemonic. 

Say what you will, but I don't think there was a single student in that class who did not "get it" the first shot, and retained it for life. 

Being the only African American in that class, it didn't bother me at all.  I was there to learn the Art of Electronics, pursuing my calling and love of the craft. 

I remember joking with the old instructor, you know, the guy with the buzz cut, glasses and pocket protector fulla pens and pencils, when leaving the class that day. 

He asked me what I was going to do that evening and I told him, "I'll be looking for that gal named Violet!" 

The one that gives WILLINGLY! 

"Be careful," he said. 

"And discreet!" I added...


73


Title: RE: Ohm's Law
Post by: VA1CQ on May 25, 2013, 12:37:02 PM
Never heard any of the above PC versions. Perhaps we were less PC in Canada. Our high school instructor taught us about the willing young Violet (though there happened not to be any women in our class) and I never forgot the colours/values.


Title: RE: Ohm's Law
Post by: K8AXW on May 25, 2013, 08:03:49 PM
DGN:  Yup..... forgot the Young Grass..... Like WD I first learned the "other" way, which I never forgot.  It's when we start throwing the PC sh.t in the game do I start forgetting things like Young!


Title: RE: Ohm's Law
Post by: KE3WD on May 26, 2013, 06:50:16 AM
The mnemonic thing was so long ago, it seems. 

Don't need it anymore really.

Like CW. 

"Here Comes the Queen" or "Diddy-Dum-Dum-Diddy"

At some point, the repetition of use kicks the little gray cells in and there is no longer any need for "decoding" or translating things in the concious mind. 

Years of dealing with the components, day in and day out, the familiarity breeds the contempt of knowing the resistor value on sight for many of the more common values, and also being able to rapidly nail the less common ones. 

Just like the day you suddenly realize that you are copying the CW ragchew entirely in your head, as whole words rather than one character at a time and there is no need for the pencil anymore. 


73


Title: RE: Ohm's Law
Post by: KB3HG on May 30, 2013, 11:02:16 AM
Had a Instructor whom had Chaplin bars on after his tests. Bill Dykes W3FRC, his 40's version for the code.....Bad Boys Romance Our Young Girls Behind Victory Garden Walls. nothing other the colors for tolerance  that I can remember now.


Title: RE: Ohm's Law
Post by: AA4HA on May 30, 2013, 01:46:31 PM
This entire argument about Ohm's law was started by some guy named Mho who was much more conductive to the idea, Ohm just kept resisting.

The old school curmudgeons got involved, those guys named Mattheisen and Jacobi but they could not remain friends. Mattheisen called Jacobi a "dirty yellow copper", Jacobi responded that at least he was not quite so ductile.

SI came on board and said that if you do not behave I will put you in different units. Eventually Mho changed his name to Siemens.


Title: RE: Ohm's Law
Post by: N3DF on May 30, 2013, 05:44:36 PM
This entire argument about Ohm's law was started by some guy named Mho who was much more conductive to the idea, Ohm just kept resisting.

The old school curmudgeons got involved, those guys named Mattheisen and Jacobi but they could not remain friends. Mattheisen called Jacobi a "dirty yellow copper", Jacobi responded that at least he was not quite so ductile.

SI came on board and said that if you do not behave I will put you in different units. Eventually Mho changed his name to Siemens.

The only question I missed on my Novice test in 1965 was "The Mho is the unit of _________________."


Title: RE: Ohm's Law
Post by: KE3WD on May 31, 2013, 05:41:25 AM
Mho, Larry and Curly...


Title: RE: Ohm's Law
Post by: W1BVV on June 10, 2013, 08:34:00 AM
At the risk of beating a dead horse and being too pedantic (I anm a Physics teacher and an Electrical Engineer), the E in older references to Ohm's law (I learned E=IR) also, came from the concept of electromotive force, or EMF sometimes written as a script E.  The electromotive force is actually the electrical potential created by a voltage source such as a chemical cells in a battery.  V, or Voltage or more accurately voltage drop or potential drop is a unit that is measured from a node to a reference (usually but not always) ground or across the two terminals of a resistor, or a battery.

Thus the voltage (V) of a battery is the voltage drop across the battery which would equal EMF (of the cell)- I*R where R is the internal resistance of the battery and I is the current being drawn from the battery.  Vb = EMF-IR.

So V, and what used to be E, and is now scriptE or EMF are very different.

There technically is no unit E, although E is the symbol for Electric Field.

Sorry,

W1BVV, Dave



Title: RE: Ohm's Law
Post by: K8AXW on June 10, 2013, 09:19:18 AM
DF:  I hope you're satisfied now! 


Title: RE: Ohm's Law
Post by: N3DF on June 10, 2013, 09:59:11 AM
DF:  I hope you're satisfied now! 

I am not.  As I near retirement, I discover that much of what I learned in high school and as a liberal arts college student was wrong or at least incomplete.  The "change" in Ohm's law is just a tiny part.  My geology course never mentioned tectonic plates.  My astonomy survey course never mentioned dark matter.  The Freudian psychology I studied is now commonly regarded as quaint at best.  "Nanook of the North" is now regarded as a poorly made almost fraudulent film rather than a fine sociological study.  Margaret Mead is often now seen as a deceived and naive woman rather than as a great anthropologist. 

I suppose my frequent and deliberate on-the-air references to condensers, megacycles and the Class A phone bands are a reaction to this. 


Title: RE: Ohm's Law
Post by: W1BVV on June 10, 2013, 10:21:14 AM
 I said "Sorry".  I too am approaching retirement.  You should see the faces on my students when I accidentally write E=IR on the board instead of V=IR.

Consider yourself lucky you don't have to deal with magnetism and have to deal with tesla's webers, gauss, and oersteds andwhich system of units they are.  It gets ugly.

W1BVV


Title: RE: Ohm's Law
Post by: W0BTU on June 10, 2013, 01:08:53 PM
and P = Power ; R = Resistance; I represents Amperes

E = Electromotive Force
The I stands for Intensity, BTW.

Is that what I stands for?

It seems to me that many years ago, I read that I stood for something else, but I'll be darned if I can remember what.

But I'll take your word for it, since I don't have a better explanation. :-)


Title: RE: Ohm's Law
Post by: KE3WD on June 10, 2013, 01:27:29 PM
It was too long ago for me also, I may be "remembering" the wrong word.  Yet again...


Title: RE: Ohm's Law
Post by: KD0REQ on June 21, 2013, 01:23:21 PM
then there's Schmo's law... if you hose up your Ohm's law calculations, all your answers are zero when the test comes back.


Title: RE: Ohm's Law
Post by: NO5J on July 06, 2013, 04:08:22 PM
The thought occurs...
If...
E==IR then why even bother with E?
IR==IR.
I think therefore, I ARE!
Maybe, I can measure just how much I ARE with my VOM.
Just tried, and got 0.0 on the LCD display.
Which could mean that I AREN'T.
But if I AREN'T then you never read this.
Unless you AREN'T?
Maybe we all AREN'T!
"It's the end of the world as we know it, and I feel fine."
Do You?

Jay - NO5J


Title: RE: Ohm's Law
Post by: K5WLR on July 06, 2013, 04:27:44 PM
My head is still spinning.... ::)  :P


Title: RE: Ohm's Law
Post by: KE3WD on July 06, 2013, 06:46:24 PM
Theoretical Physicists are indeed tackling the idea that this is a holographic universe...


Title: RE: Ohm's Law
Post by: G3RZP on July 08, 2013, 01:05:42 PM
isn't 'omes law' government housing policy?