Are Voltage and Electromotive Force the Same

[@robertbates4682]

you are a master of your craft

[@mikemac687]

You do an excellent job of explaining and illustrating your theory. I wish I had you as a teacher! I watch a lot of your lectures. Thank you for giving your expertise to the public.

[@ulyssesfewl1059]

At 12:47 no, there will not be 1/360 of a volt per degree. The "voltage" anywhere in the ideal conductor will be the same and it is only across the resistor that the 1V is dropped.

[@trevorkearney3088]

This video highlights the problem of claiming a physical result without attempting an experimental verification. At about time 8:40, Bob claims a voltmeter connected between two points on the conducting resistance wire loop would indicate zero volts. This is incorrect. The voltmeter would indicate the Ohmic voltage change along the partial loop segment adjacent to and spanned by the connected voltmeter. The solenoid winding producing the time-varying magnetic flux would need to be of a long tightly pitched construction. Such a construction usually ensures that the magnetic field flux external to the solenoid boundary near the closed resistive wire loop would be negligible, compared with the internal magnetic field flux within the solenoid winding boundary. One would loop the resistive wire around the longitudinal geometrical centre point of the solenoid winding. In that configuration electromagnetic induction in the resistive loop is not attributable to flux cutting - rather to flux linking. What drives the current in the loop? This is attributed (in physics texts) to a non-conservative circulating induced electric field which appears outside the solenoid boundary, coincident with the resistive loop path and having there a tangentially aligned field strength inversely proportional to the radial distance from the solenoid axis. See the video linked below for an explanation: kzbin.info/www/bejne/oHqmmoiMhsSEoa8feature=shared Other than in a transformer, are there practical applications where the electric field associated with a time-varying magnetic field is utilised? The Betatron is an early example of a particle accelerator in which a narrow beam of electrons circulate within an evacuated toroidal tube. The electrons are accelerated by an azimuthal non-conservative electric field associated with a time-varying magnetic field acting orthogonally along the toroidal tube major axis. The same magnetic field is also involved in bending the electron beam so that it follows a circular path within the toroidal tube along the torus mean radius.

[@nix9409]

I was just thinking about this very thing today and over the years, but unless the wire is superconducting, assuming it is of uniform resistance, we can measure a voltage drop, we can imagine that loop of wire as bunch of resistors in series, so it is possible to measure voltage drop between two points aka across one of those imaginary individual resistors. This is easy to prove using high resistance wire like tungsten or nichrome as a single turn secondary, as we induce the current through it, let's say we use high frequency so that voltage is higher and easier to measure, we can measure the voltage drop across parts of the loop.

[@kailashspidel9647]

Isn't the example of a coil of wire still a conservative force? If the generator were to be turned off the magnetic field would collapse effectively applying a voltage back to the generator, turning it into a motor ( briefly). Or am I way off? Thanks

[@Vocademy-Electronics-Tech]

A coil of uniform resistance forming an unbroken loop will be non-conserative. However, if the loop is broken or the resistance is not uniform, the voltage gradient in the loop is conservative. You are correct on your second question. Try this: take a small DC motor and spin it. See how freely the armature spins. Now short the power connections together and spin it again. Not it stops spinning quickly. That's the motor acting as a generator producing current that tries to turn the motor in the opposite direction.

[@trevorkearney3088]

In your discussion concerning a closed conducting loop enclosing a continually increasing magnetic flux with a voltmeter attached to two points on the conducting loop, you state that there is zero voltage difference between the two points - or any two points for that matter. You then state the voltmeter would indicate zero volts. Unfortunately this thought experiment is rather ill-defined. At one point you state the loop could have zero resistance. What would be the induced loop current in that case? Would it increase in an unbounded manner? What would be the effect of the self-induced magnetic field due to the circulating loop current? Is the expanding primary magnetic field confined to some region of the space near the wire loop or does it increase into the entire surrounding region? One would have to definitely consider the effect of the increasing magnetic field on the measurement topology. As an alternative thought experiment, consider the case of a highly permeable toroidal ferrite magnetic core in which a confined increasing magnetic field is generated via an increasing current switched into a primary winding on the core. The core would eventually saturate, but we could make some observations (say using a CRO) over a short time frame following the energising of current in the primary winding. Consider now a closed secondary loop of resistance wire passing through the core window. We therefore have the secondary loop enclosing the confined increasing magnetic flux in the energised core. Consider now a CRO vertical input channel connected between two points on the single turn resistive wire loop. Suppose the primary winding is energised with a short duration transient step voltage at some arbitrary time zero and induced current begins to flow in the single turn secondary wire loop. What is indicated on the CRO if it is triggered concurrently to start capturing the resulting voltage between two disparate points on the loop? The CRO display certainly won't be indicating zero volts over the short duration test cycle. As a final comment it is a well established axiom of classical electromagnetic induction that the physical entity that drives current flow is the non-conservative electric field that arises together with the time-varying magnetic field. Electric potentials and voltage gradients observed in material media are the result of electric fields acting on unbound electric charges in the material body.

[@leonhardtkristensen4093]

As I understand you right now then you are correct in your statments. A fev comments disagree a little. What I think may help your explanation is that it is possible to have a current without a messurable voltage. It is 100% kinetic energy and I would believe a super conductive closed coil (ring) will keep it's current until either taken out or the super conductive area or it is magnetially removed . I would believe though that a normal ring with resistance that will get hot with a current would some where have a potential allthough I suppose it could be across and definitely on the atomic level. It is basically what you have in a pot on an induction stove. P=I*I*R=U*U/R Is there any way to get out heat energy without resistance? If no then there must also be a voltage however small.

[@sputnik4216]

Your videos are great! I've watched a bunch and that white reflection on the whiteboard just left and below dead center is driving me crazy because I keep thinking it's my monitor pixels going bad! I particularly liked your video on toroid core compared to solenoid. As far as that one, my opinion is that it's comparing apples to oranges. The toroid is not a solenoid, solenoids are unique in and of themselves. Your toroid example is acting as an inductor, but becomes a transformer when you put the 'completed' winding through the core's center. Incomplete, it's just like some stray piece of wire that cannot couple to the toroid's unique field. The toroid has no N/S, it is continuous. This experiment would be the same using a typical iron transformer that you could sneak a wire through similarly. Just my 2 cents.

[@trevorkearney3088]

Actually if one considers the self inductance of a "long" solenoid winding vs a toroidal winding having an equivalent mean major circumference, wound over identical high permeability core materials of equal diameter and with the same number of turns, the inductances are very close. For instance a 300 turn toroidal inductor wound over a core of major mean radius 5 cm, minor radius 1cm and relative permeability of 200 would have an inductance of around 22.6 mH. A 300 turn solenoidal inductor wound over a core of length 31.4 cm, radius 1cm and relative permeability 200 would have an inductance very close to the toroidal inductance. I would would envisage the toroidal winding simply as a solenoidal winding formed into a closed loop. You are correct that a toroidal inductance can be viewed as a transformer when a secondary winding is added. Toroidal transformers are quite common. The benefit of a well designed toroidal inductor (transformer) is that it has negligible external magnetic field at low frequencies (e.g. an AC mains transformer). The B field is ideally confined within the highly permeable core material. Many people are then at a loss as how to explain induction in a secondary winding with a negligible B field outside the core. While there is a negligible external B field, there is a substantial external vector potential field which is the agent of induction in the secondary winding. James Clerk Maxwell proposed the existence of the magnetic vector potential and its role as the agent of electromagnetic induction. The Aharonov-Bohm experiment is believed to be a modern confirmation of the existence of the vector potential. Early engineers (such as Oliver Heaviside) were unconvinced of the reality of the vector potential, viewing it merely as a useful mathematical construct. In the case of the toroidal transformer the vector potential field is more concentrated within the core window and hence a substantial part of the induction occurs within the core window. But the vector potential (and hence induction) still exists to a lesser extent outside the core window. Bob is incorrect in his belief that the induction is confined to the core window. It occurs to varying degree along any closed path which encloses the core - which of necessity transits the core window once for each secondary turn. If you wish to explore this further there is an excellent paper available on the web entitled "On the fields of a toroid and the role of the vector potential" by Neal Carron. Carron clearly develops the theory of the fields associated with a toroidal winding. Carron does show that with a primary sinusoidal time-varying inductor current there will be a radiated magnetic field external to the toroidal winding - but this radiated near-field field is of insufficient strength to account for any secondary induced EMF.

[@Tmas-o5y]

You don't need the resistor. The impedance of your measuring device does the same thing. The only difference is the amount of current that flows. Can you ever measure a force? I would say you can only ever measure its effect.

[@MrDoneboy]

What about, The potential difference between two points, as Voltage...And EMF?

[@Vocademy-Electronics-Tech]

That's my point. The entity engineers call EMF or voltage differential and physicists call V, is not the same that physicists call emf or Ꜫ. You cannot measure Ꜫ with a voltmeter.

[@MrDoneboy]

@@Vocademy-Electronics-Tech Thanks again, Bob! Doing my best to get you more subscibers!

[@carultch]

@@MrDoneboy Voltage is an informal name for anything measured in Volts. Engineers commonly default to the term voltage, even though physicists have more formalized names. Electric potential is a special case of EMF, when the field is conservative, and the concept of electric potential works in our favor as a shortcut for evaluating the EMF. In general, EMF is the work done by a field, per unit charge, as a charge moves between two points. It is a line integral of E dot dℓ, where E is the electric field, and dℓ is the infinitesimal incremental distance along the path. Given a purely electrostatic field, i.e. a field set up by stationary charges, the closed loop integral E dot dℓ is zero, and the integral E dot dℓ is independent of path. It only depends on the start and end points of the charge's motion. We define electric potential to be this potential function of space, that pre-evaluates this formula as a shortcut for us. We chose a reference point that we define as zero potential, and evaluate this integral to each of the points in space, each starting at that reference point. Usually, the reference point is either ground, or infinitely far away. This is the kind of potential that defines what we normally think of as voltage, and what we use for evaluating Kirchhoff's voltage loop law. Since closed loop integral E dot dℓ is zero, the sum of voltage differences around any loop is also zero, in this special case. When Faraday's law of magnetic induction is also involved, the field is no longer a conservative field. Closed loop integral E dot dℓ, no longer equals zero. Instead, it equals a value that is determined by the rate of change of the magnetic field, and the area it covers. This is what is meant by EMF, when we contrast it from electric potential. It is no longer valid to just evaluate electric potential at the initial point and final point, to determine the work done on the charge. The work done is path-dependent, and so is the voltage induced in the circuit.

[@atheistaetherist2747]

Everything is photons. There is no such thing as a solid little nut (electron) orbiting a nucleus. Hence the problem of radiation during acceleration duznt exist. In an atom, what we have is a photon orbiting a nucleus. Let us name this an elektron. It has a negative charge. It radiates, & radiation needs energy. But, that radiation is little different to ordinary radiation that radiates from every photon all the time for ever. The energy comes from the aether, we dont know how. Elektrons migrating along in a wire give us (a slow) elektricity. When a photon forms a loop (by biting its own tail) then it makes an electron. Electrons have a negative charge. Electrons can sit on & migrate on a surface -- or fly throo space - they give us static charge -- & movement (on a surface)(or through space) gives us (a slow) electricity. The acceleration of an electron needs the input of energy. And apparently the acceleration of an electron needs additional input of energy to replace energy radiated by the acceleration. What standard science calls electricity in a wire is actually due to photons hugging the surface of a wire. Let us name these elektons. Elektons have a negative charge. Elektons propagate at the speed of light, & give us (fast) elekticity. Elektons & elektrons propagate at the speed of light all the time for ever, so in that sense there can be no acceleration of the propagation. But, elektons & elektrons can be made to change course or move or migrate. And, we have (fast) Elekticity, & (slow) Elektricity, & (slow) Electricity -- 3 kinds. And we can add the ionic form of (slow) electricity, where negative ions migrate -- this needs a new name -- iontricity praps. And we can add the positive ionic form of (slow) electricity, where positive ions migrate -- this needs a new name -- positricity praps.

[@keylanoslokj1806]

Cut the shrooms bro 😂

[@atheistaetherist2747]

@@keylanoslokj1806 magic.

[@62twinturboImpala]

I was taught Emf or E(sub)mf to represent Electromotive Force and E for Voltage. In later years E or V for Voltage.