Ohm's Law: History and Biography 

Thank you so much and especially thank you for forgiving my bad pronunciation I am trying it’s just very difficult for me for some weird reason.

@@Kathy_Loves_Physics The easiest and fastest way is to use Google translate's text to speech function. Just type in It is fairly accurate or german words, so I highly recommend you to chekc it out. Love your videos!

Ja, wohl. However Kathy also has a habit of mispronouncing many less common English words. (I'm American and I assume from her accent that Kathy must be North American. There are differences in pronunciation between British English and North American, but that's not the issue. ) I agree, Kathy's videos are fascinating and worthwhile. I'm a 71 Electrical Engineer, and enjoy her elucidations of the history and personalities.

@@Kathy_Loves_Physics Many "science type" people (my wife is one) have an immense vocabulary that they learned at an early age from reading, not from listening. They will thus have invented their own pronunciations of certain words in English and other languages. My wife, a chemist, had to learn German so that she could read Beilstein (the famous compendium of organic compounds). Her pronunciation of German is atrocious, scheußlich, grauenhaft. I, on the other hand, learned German poetry and songs, and put much effort into correct pronunciation. Now as I learn Spanish I find it very easy to pronounce it correctly, to the point that I am asked, "How long did you live in Mexico?" (Never been there!) Now I must put that kind of effort into grad, div, curl and Maxwell's equations that I never learned well so many years ago.

Davide?

Shocking

Great pun!

I guess the established scientist’s weren’t all to amped up about the new theory

Ohm my!

So much tension !

He was a high school teacher but it didn’t go down exactly like that I was actually trying to link electricity and magnetism for eight years I think at the time. I have a video about him of course, you should check it out

@@Kathy_Loves_Physics you were trying to do that? :D

Electricity and magnetism are two separate phenomenon that influence the ether in very similar manners but are distinctly separate after all magnetism is structural and is produced by the structure of the compound, electricity is motion of the etheric fluids derived from luminoferous ether.

@@sebastianstewart6894 ether isnt a thing, I have to disappoint you

@@lugyd1xdone195 yeah, SS is seeing the ether bunny.....

I never knew that quote, I love it. (I also am a big fan of Max Planck, I’ve made think five videos about him and I’m planning a book about him and his influence).

@@Kathy_Loves_Physics Max Plank was the first famous physicist to champion Einstein, I am given to understand. Just discovered your channel. Possibly nothing interests me as much as the history of science. The flat Earthers have gotten me thinking about how a layman can prove a spherical Earth to a skeptic. Not easy at all. The common description of ships disappearing over the horizon only proves the curvature of sea level.

"...Charles Wheatstone who bridged the gap..." had me genuinely laugh out loud.

was looking for this... and I am not disappointed... Great pun hahaha

Yep, I paused the video and came looking for the comments! 🙂

OHMS LAW IS SIMPLE ON DC ,,,, on AC THE THINGS BECAME UGLY because in DC you work with R , on AC you work with Z ,,,, IMPEDANCE ,,,, not RESISTOR

@@lesstime1678 - Ohm's law is simple with AC, but who was the one that figured out it was simple?

Ambient temperature C/F is a factor of conductivity and resistiviity.

@@jrstf Ohm’s law is actually a bit more complicated with AC than DC. With DC, except for the moment of turning power on or off, the resistance to current flow, and thus the current, is steady because the voltage is steady. With AC, specifically with sine waves (where voltage and current vary in proportion to sin(2•pi•f•t), where f = frequency in cycles per second, or Hertz (Hz), and t = time), there are three factors other than voltage that affect current: resistance, inductance (the effect of a changing magnetic field on the conductor from which it is generated, which “resists” changes in current), and capacitance (the effect of an electrostatic field to “resist” changes in voltage). The latter two create an effect called “reactance,” which like resistance is measured in ohms, but they cannot be simply added! A theoretically pure inductor has a reactance that varies with frequency, XL = 2•pi•f•L, where L = inductance in henrys (after Joseph Henry). This inductive reactance restricts the AMOUNT of current, but it also causes the graph of current vs time to LAG the voltage by 90 degrees, or 1/4 cycle. So current is at a negative maximum when voltage is crossing zero from negative to positive, going from negative to positive when voltage is at its positive peak, at its negative peak when voltage is crossing zero from positive to negative, and crossing zero from positive to negative when voltage is at its negative peak. Therefore, resistance and inductive reactance are added as 2-d vectors (aka phasors, which are not Star Trek weapons) phased 90 degrees apart, with the phasor sum being the diagonal, having BOTH intensity and phase angle (between zero and 90 degrees (or -270 degrees). For this reason, actual inductors (if capacitive reactance is insignificant) produce a resultant “resistance” with a phase angle between zero and 90 degrees. And the higher the frequency, the more reactance, while resistance remains steady (except for “skin effect,” which keeps current from flowing in the interior of a conductor at higher frequencies). A capacitor, on the other hand, does the opposite: ignoring the resistance of actual capacitors, the CAPACITIVE reactance causes current to change 90 degrees AHEAD of voltage, and restricts the flow of AC in a way that is INVERSELY proportional to the frequency (actually, current doesn’t REALLY flow across a capacitor, since it is an open circuit, but the electrons in each plate can “feel” the attraction or repulsion from the opposite plate, so variations in current flow can pass through). This capacitive reactance XC, also measured in ohms, is at a phase angle of -90 degrees, or 270 degrees, and its magnitude is 1/(2•pi•f.C), where C = capacitance in farads (after Michael Faraday). So to combine resistance and reactance in series (or in the same component, known as “parasitic” resistance, capacitance, and inductance), to get the phasor value Y, aka “impedance,” just sum up the values AS PHASORS: Y^ = R^(0 degrees) + XL^(90 degrees) + XC^(-90 degrees) AT A SPECIFIC FREQUENCY. To combine these values in parallel, add their reciprocals in mhos (or siemens). The reciprocals have unique names: the reciprocal of resistance is “conductance,” the reciprocal of reactance is “susceptance,” and the reciprocal of impedance is “admittance.” Note that at low frequencies, inductive reactance is smaller (for DC, it’s zero) and capacitive reactance is larger (at DC it’s infinite!), so the current is small and lagging behind voltage; at high frequencies, inductive reactance is higher, and capacitive reactance is smaller, so the current is small and leading the voltage. At some in-between frequency, inductive and capacitive reactance cancel out, and the current is at a maximum and in phase with the voltage. This is called RESONANCE, for a series resonant circuit. Note that the voltages across the inductor and the capacitor are MUCH LARGER than the power supply voltage, and are 180 degrees out of phase with each other! A common mnemonic to remember these phases is the phrase “ELI the ICE man,” meaning “E (an alternate symbol for V) in an L (inductor) leads I (current intensity), while I in a C (capacitor) leads E.” One reason Edison distrusted AC was the more complex math; he was, after all, a self-educated genius tinkerer!

@@colmcillegardner2144 - That is true but is not related to Ohm's Law.

Thanks

WELL SAID...I TOTALLY 2ND THAT!!!

@@Kathy_Loves_Physics I love the way you explain a lot with your hand gestures 👍👍I tried going into portrait mode to see more.😉😊

Do you like mashed potatoes?

@@glennasaurus81 it's all about the milk when talking mashed potatoes

Not milk. Heavy cream! and about a pound of butter!!

@@mashedpotatoes5323 Yes with plenty of countrylife butter and some full cream milk. 😋 😋 😋

Wow! EEVblog is here too! Love you channel too😁

Well: No engineer thinks about ohms law in practice, as it is to intuitive, obvious and simple to call out as such. But many calculation have a result or and input in ohm - so his name is honored a lot. Tesla on the other hand got the short stick, but that makes him the hero of all nerdy underdogs.

Worse yet, as we see in todays cov id crisis, politics plays a huge role in science. Something that should not be the case. It's sad that science was one of the first casualties of the pandemic.

well, artists are a bit different. When they die, they can no longer produce more pieces, so the price starts to go up.

@@1pcfred he would have been financially rewarded properly had he not completely surrendered his rights to electricity royalties from westinghouse

@legg The unit of magnetic field strength is the Tesla.

It’s better than the way you pronounced Marconi’s first name😂, great vid, keep em coming, yes to Wheatstone 👍

I understand it might be too much work, but I guess I talk for must of us. Thank you for your replies. 🌹

@@theklaus7436 you are welcome. I like replying to nice people

While we are on the subject, Rutherford is pronounced ru-their-furd 😀

@Science Revolution, really, dude? Have you made this observation from space? You realize that the ocean is made of water -- right? And that it doesn't have to maintain the same level everywhere, depending on the force(s) acting on it -- right? Have you measured the thermal cycling of the landmass? If you do, you'll find that your idea on the matter are nonsense. But hey, in these post-modern times, whatever you want to believe is your personal truth, so hey, gratify yourself.

Thanks. I always find it frustrating when biographies say “people believed x but famous scientist did not” without telling why.

I’ve been shocked at how many times looking into the history of something I felt like I understand inside and out made me understand it in a deeper way. Glad you feel the same way.

But it currently has power.

@@1SnuffySmith Lmao, please there's the door!

I know, I know...even I'm cringing at what I typed.

Sorry to be a pedant Timothy, but “cycle per SECOND” is now known as hertz 😉

@@timothystockman7533 Sorry to be pedantic again (!) Timothy, but one could never say that the ACTUAL UNIT itself is IRRELEVANT notwithstanding the fact that in everyday engineering parlance, it was abbreviated to “cycles” for convenience. It was NOT cycles/minute or cycles/hour, but cycles/second, so yes, it is entirely relevant. Just as, for example a 27k resistor or a 10u capacitor are both abbreviated, the actual units are still “ohms” and “farads”. Your original point was that the old term for conductance, “mho” is now “Siemens”, which is of course absolutely correct. I was stressing that, strictly speaking, “cycles per second” is now Hertz, not “cycles”, regardless of how it was abbreviated amongst electronic engineers and technicians.

The deeper you get down the rabbit hole, the more interesting it get's. When I learned that stuff in the 1980s we uses siemens, never heard of mho before. And now I just found out that there was even an unit of resistance called "Siemens mercury unit" that was defined in 1860, which was then superseded by ohm (Ω) in 1881. And it seems that even publications that name the unit siemens sometimes use ℧ as the symbol when there could be mix-ups because of the letter S.

Thanks not correct. Conductance is the inverse of resitance. Suspentance is the inverse of Reactance and Admittance is the inverse of impedence which is the Mho that is now called Siemens.

@@jeffreydove2036 Of course, you mean Susceptance not Suspentance ....

Thanks

Also, how long it took to get agreement across nations! I recently watched a valuation of an restored antique Ohmeter on a TV show (Bares für Rares) where the expert could date the model to 1898, as the omega symbol on the dial was first officialised in Germany that year, 40 years after your date for Britain. it was a beautiful hardwood box, but more in your tinkerer's category. It used the earth's magnetic field as a constant source. That meant it needed to be aligned in the magnetic field to calibrate the readout. Thiis is anecdotal, the expert could have been wrong, the dials added later during restoration, for example. But decades to cross the North Sea and further decades for the symbol to return are a long time, in any event.

A book that describes the opposition to new ideas is The Structure of Scientific Revolutions by Thomas Kuhn.

@@c_b5060 Kindle is wonderful

Another book is The Cosmic Serpent.

So many good puns… so little time

13:10 “..there was an engineer named Charles Wheatstone who bridged the gap..”

I talked a bit about Kirchhoff in my video about the history of spectroscopy but not about his law specifically. Did you know he made that law when he was a college student? Crazy!

I assume you substitute the mercury with a Gallium alloy? I would assume, that Ohm used a mercury alloy, as solid metal touching liquid metal always leads to an exchange, so "over time" the mercury had to become an alloy.

@@sarowie She has already ordered some gallium. What Ohm did was to coat the copper of his apparatus with varnish where it went into the mercury then filed the end of the bars before dipping them in the mercury in small cups (he had the cups on a platform that was raised into position and locked there). This gave a constant area of clean copper when it was immersed in the mercury. This was because there was no industry producing a means of making good connections in electrical circuits and he was trying to reduce the experimental variables as much as possible.

Siemens is more commonly used outside Germany as well, at least in the Western world.

Glad you liked it

Good Idea!

@@Kathy_Loves_Physics I see you did that already, that's amazing! Thank you so much!!

@@lorenzobarbano of course, thanks for reminding me

No doubt a terrific conversation starter!

I’ll try but that sounds daunting

@@Kathy_Loves_Physics 😁😁😁

Thanks

Thank you

Thanks- I’m a little obsessed

You are welcome.

I was pretty surprised when I bumped into her myself

Glad you enjoyed it!

Thank you.

Conductivity used to be in units of mhos, ℧, but now the unit is Siemens, S. It's still the same quantity 1/R. Sort of like Hz used to be called cycles per second, c.p.s.