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Electron Flow vs Energy Flow? - Help me understand

Discussion in 'General Electronics Discussion' started by Mikey32230, Oct 4, 2015.

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  1. Mikey32230

    Mikey32230

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    Aug 21, 2015
    Hi,

    I have recently become very intrigued by electronics and how things actually work. I've recently graduated with a degree in MIS, but never took any classes to learn about electricity / engineering, etc. So i am no longer a student, but I am taking on electronics as a hobby, and want to continue to learn.

    I find it fairly difficult to get a good grasp on understanding "electricity". From studying on my own I have learned about electricity & circuits by using water flow, pressure, pipes, values etc as an analogy. While this is a great analogy to introduce people to electricity, it has caused my lots of confusion as I continued to further comprehend core topics. I have just finished reading several lengthy documents to help wrap my head around misconceptions. I feel I am close to a light bulb going off in my head about electrical circuits in general.

    Can someone please critique, confirm, fix my current thoughts/questions/misconceptions below?

    Given a simple circuit that contains a light-bulb and is "powered" by a normal 1.5v battery:

    When the circuit is closed, electrons are pushed out of the "negatively charged" end of the battery by voltage. Voltage being a sort of pressure built up where electrons in the wire itself begin to slowly seek/tend toward the positive end of the battery due to a voltage potential difference. The movement (Distance traveled) of the electrons is relatively slow, however, their vibrations create EM energy. This EM energy flows one direction? It flows from the positive end of the battery to the negative/ground?

    If this is the case, the energy (in this case) is flowing opposite the electrons?

    If the above 3 questions / statements are true, I am confused about "ground". Don't the electrons seek ground (0 Volts)? In some circuits the return /negative side can be connected to ground (earth ground). If the electrons original from the negative side wouldn't they tend to flow to ground instead of the positive end of the battery? Or is it the EM energy that flows from Positive to Negative that wants to reach ground?

    As you can see, I am quite confused about this topic and I need some good clear guidance to help me understand. I think i am stuck/confused between different conventions I have come across.

    Please help if you can :)
     
  2. Minder

    Minder

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    Apr 24, 2015
    I can see why you are confused in a couple of areas.
    Read up on electron flow and conventional flow.
    I was raised, electronically speaking, during the valve/tube era and had a grasp on the electron flow from cathode to anode, but supposedly accredited to Ben Franklin, electron flow is from positive to negative ( now conventional flow).
    This is also why the symbol for a diode, which is a classic check valve, is backwards AFA electron flow is concerned.
    On the question of ground, in N.A. the term 'ground' is used for both Earth ground and power common, rather than other parts of the world that use the term 'Earth' when referring to a earth grounded conductor, rather than a power common.
    This is further confusing for students that use the Art Of Electronics etc that show misuse of the earth ground symbol throughout the book instead of the Common symbol.
    A good read on it.
    http://www.ese.upenn.edu/rca/instruments/misctutorials/Ground/grd.html
    M.
     

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    Last edited: Oct 4, 2015
  3. davenn

    davenn Moderator

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    yes, the water/pipe analogy fails pretty quickly


    the EM field is moving in the same direction as the general movement direction of the electrons
    the EM field is also on the outside of the conductor and is the principle energy carrier in the circuit

    sort of ok but badly worded ... its all about the potential difference between the battery/power supply terminals
    They are not pushed out of the negative terminals as such. Once the circuit connections between the
    battery terminals is made, electrons start moving into the + terminal attracted by the positive ions at that terminal

    what ground ?? in your simple battery and bulb circuit there is no ground.. the electrons will be "attracted " by an opposite charge :) And even if you did connect a ground, it's not going to stop the electrons moving from the term, through the cct and to the + terminal ... They have no reason to go anywhere else
    try it
    make a battery and bulb cct ... note the bulb lights up
    now connect an addition wire from the - term to a metal rod into the ground ... your lawn/garden soil
    note the bulb still lights up

    Dave
     
    Last edited: Oct 5, 2015
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Imagine that someone from space saw a stream of trucks moving between two buildings. The buildings were each partially full of water, and as each truck arrived and departed the level of the water decreased in one and increased in the other. From space, the observers decided that the trucks were taking water from one building to the other and decided that the flow of goods was in a certain direction.

    However, they later discovered that what was being moved was actually hydrogen, and it was displacing the water.

    However, they had already determined a conventional flow (that of the water) and continued to use it, even though the real flow was in the opposite direction.

    This is how it worked with electric current. It was observed that charge was moving from place to place, and in a coin flip they decided it moved from what they had called positive (an excess) to what they had called negative (a deficit). Later, when they found that the charge carriers were actually the opposite from what they initially guessed, the conventional flow from positive to negative was entrenched.
     
  5. GPG

    GPG

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    Sep 18, 2015
    Ground is a convention that gives a reference to measure voltages and current relatively. In a circuit ground may or not be actual ground. and ground may not be 0V.The energy travels faster than the electron speed.so
    https://en.wikipedia.org/wiki/Speed_of_electricity
    Don't know if this helps or makes things more confusing.
     
  6. Minder

    Minder

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    As per Dr Bruce Archambeault (#2).
    The term 'Ground' is simply too ambiguous!.
    M.
     
  7. Mikey32230

    Mikey32230

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    Aug 21, 2015
    Thank you all for your answers :) each one helped a little!

    Lots more questions, but getting closer :)

    Okay, I read that the EM field didnt have to move in the same direction as the electrons (as in the case of AC where the dont really move anywhere, just vibrate). But in the DC example above, it makes sense that it would move in the direction of the electrons. If this is the case, does our simple circuit actually run backwards? Does the light actually light up from (-) side to (+) side, generally speaking? If we made the simple circuit slightly more complex and added a diode on the negative side of the circuit (forward bias like normal) how do the electrons / energy pass through the diode to light the light? The example I have described is how it would be done in real life and it follows the water/pipe analogy. It is set up with the assumption that current begins to flow from positive to negative. Are diodes & all other components sort of "secretly" designed opposite the normal positive to negative design?

    Can you give me a simple sort of definition for potential difference in the way that makes sense to you? It does make sense to me that the electrons move from the - terminal to the + terminal based on attraction. Should I think of the battery as having a bunch of protons in the positive side and a bunch of electrons in the negative. The electrons want to repel each other as well as attract to the positive end. Is there more protons on the + side than electrons in the - side? Is that what the potential difference is? If this is the case, why dont the protons want to repel each other also and meet the electrons somewhere in the middle of the circuit?

    I also read that the battery isn't really introducing / creating any electrons. The electrons are already in metal of the circuit's wire. If the battery isn't really introducing electrons then what is it doing to push / pulling them through the wire? And if the electrons from the wire are being attracted to the positive end, why doesn't the negative side of the wire run out of electrons?

    What is the point of ground then? I know ground has several meanings depending on context. One is earth ground, which is what I was talking about above. Why do the electrons want to go to ground by default if there is no opposite charge to flow to?

    Say we Earth grounded my simple circuit, how does that provide safety? and does it matter where you put the ground wire? what's the difference between putting it somewhere on the positive side vs somewhere on the negative side?

    What is the other context for ground? I keep seeing people say it is used as a reference point .. like:
    I have read about it numerous times but I cant quite come up with an analogy or way to understand it.

    Also, I am reading through this right now, and looks fairly promising. This might help me out with ground a little bit.
    Sorry for all the questions, I just want to get this down, and Im very curious.

    Thank you!
     
    Last edited: Oct 5, 2015
  8. Minder

    Minder

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    Ground as it pertains to a circuit diagram is a simple common reference point only, typically the neg side of a supply and used as a common point where circuit signals or voltages are referenced from.
    It could just as easily be any other point such as the +rail of a supply.
    In the case a Earth ground it is a point of a circuit or supply that is also referenced to earth (the planet) as a means of safety.
    Electrons only flow to earth ground if some point of the power supply is referenced to earth ground.
    The concept of Earth ground is explained in the U of Penn reference.
    M.
     
    Last edited: Oct 5, 2015
  9. Ratch

    Ratch

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    That is because there is a lot of BS (Beautiful Sunshine) around, both verbally and in print, bemusing you and others. But not me, however.

    Do your circuits leak? Do you get wet when you work with or study them? Tell me, do hydraulic engineers study electrical circuits to learn their craft? If not, why should you study hydraulics to learn electronics? Why not learn the principles directly and throw away those crutches and walkers? Analogies are only good for illustrating a narrow point, not showing how something works.

    NO. Voltage is not a "pressure" (force per area). It is an energy density. Charge carriers of the same polarity repel each other. It takes energy to gather them together. It takes more energy to gather them together in a smaller space. It takes even more energy to gather more charge carriers into that same space. Voltage is the energy per charge density, expressed in volts, whose MKS unit is joules per coulomb. When a voltage difference is applied across a conductor, the charges will flow from the higher voltage (energy density) to the lower voltage.

    Slow and fast pertain to velocity, not distance. The velocity of the electrons in a conductor is very fast due to the scattering in all directions of the path, but the average or drift velocity along the conductor is very slow.

    The charge carriers transfer energy, not the EM fields. The battery has to supply the energy to move the charge carriers through the conductors. The components in the conduction path (like resistors) surely are not going to supply energy to the battery.


    If you are pulling a weight along the ground or pushing it, are you not supplying energy to the friction of the weight in both cases?

    What does ground have to do with the veracity of those questions?

    Yes, you are really confused. Ground is just a convenient point of conduction, usually where several circuits come into contact with each other. It means no more to the charge carriers or the battery terminal than any other point on the circuit. It is the voltage which determines where the charge carriers flow. Ground is often defined as 0 volts, but it doesn't have to be.

    I see in some of the answers you received that you have been introduced to a couple of methods of calculating circuit values. They are quite confusing both in name and method because they want to presuppose a polarity for the charge carrier. DON'T DO THAT! Use what I call the (conventional) mathematical method for both polarities of charge carriers. Always assume that a positive charge carrier will come out of a positive voltage no matter if the charge carrier is a electron, positron, hole, cation, anion (in electrolysis), or whatever. Then, if you really have to know the direction of the charge carrier, reverse the direction of your calculation if it is a negative charge carrier, and leave it be if it is a positive charge carrier. If you try to presuppose the polarity, you can really get your mind wrapped around the axle.

    Ask some more questions.

    Ratch
     
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  10. Mikey32230

    Mikey32230

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    Aug 21, 2015
    @Ratch

    Thank you for your answers. I did ask some more questions, above. (#7) here
     
  11. davenn

    davenn Moderator

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    that's incorrect .... the EM field oscillates back and forward with the motion of the electrons

    DONT FORGET ... its the accelerating charges ( the electrons) that produce the EM field (wave)
    so if the charges are changing direction ( as in AC ) then so is the EM

    so scrap everything else you said in that big paragraph of yours

    for anyone who say's an EM field doesn't carry the energy, had better explain how a radio wave works if it doesn't carry the energy either in free air or in a waveguide. THE EM FIELD DOES CARRY THE ENERGY

    note the very last sentence I typed that you quoted for this comment of yours

    do you know what a positive ion is ? ... it's an atom with a few electrons missing. It isn't just protons on their own

    for every electron that leaves the wire ( circuit) one comes into the wire to replace it

    correct... the electrons already exist in the battery .. the chemical action in the battery separates the charges ....
    negative charges (electrons) to the negative terminal. Positive charges ( + ions) to the positive terminal
    That is the creation of the potential difference across the battery


    it is introducing electrons to the circuit .... but as I said before, for every electron that enters the circuit, one leaves the circuit

    And if the electrons from the wire are being attracted to the positive end, why doesn't the negative side of the wire run out of electrons? [/QUOTE]

    A battery goes flat doesn't it .... why do you think that happens, based on what I said a couple of comments ago ??


    Dave
     
  12. Mikey32230

    Mikey32230

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    Aug 21, 2015
    Okay, the way you worded that definitely helped! I think I now have a fairly clear understanding of the battery as a circuit power supply now.

    Your responses to some of my other questions, didn't quite help me get the answers I was trying to grasp.. Probably because I'm doing a poor job translating what I read & interpreted during self learning.


    I had previously sort of equated the EM field produced by the electrons to the Energy. In my head I was basically thinking "EM Field is analogous to THE electric energy". So from what you just wrote.. I must not be far off in my thinking. The article I read said this "Electric energy can even flow in a direction opposite to that of the electric current. In a single wire, electric energy can move continuously forward while the direction of the electric current is slowly backwards. In AC circuits the energy flows continuously forward while the charges are alternating back and forth at high frequency. The charges wiggle, while the energy flows forward; electric current is not energy flow." Source

    The other questions I posed in that paragraph are things I am definitely confused about and it would be a great help if you could address them directly. Here is is again:
    1) Does our simple circuit actually run backwards (sort of)?
    2) Does the light actually light up from (-) side to (+) side, generally speaking?
    3) If we made the simple circuit slightly more complex and added a diode on the negative side of the circuit (forward bias like normal) how do the electrons / energy pass through the diode to light the light?
    4) The example I have described is how it would be done in real life and it follows the water/pipe analogy. It is set up with the assumption that current begins to flow from positive to negative. Are diodes & all other components sort of "secretly" designed opposite the normal positive to negative design?

    I did some more reading between the time I wrote those questions and the time you responded. From what I gathered, it sounds like circuit diagrams and schematics are depicted based on Conventional Current as opposed to Electron flow. Its almost like we have to read the diagrams and then just know that everything is actually opposite? the current flows from the negative, the diodes are actually biased the opposite directions.. etc.

    I took note of the last sentence you typed from that quote, I understand "Once the circuit connections between the battery terminals is made, electrons start moving into the + terminal attracted by the positive ions at that terminal." The electrons move based on attraction to positive ions, got it! but my question was asking why the positive ions dont also move toward the electrons.. aren't they also attracted to their opposite charge?
    ... Well I think I might be able to sort of answer my own question here thanks to @Ratch . Its because of the voltage difference, charges will flow from the higher voltage (negative side) to the lower (positive side). The positive side ions cant flow up to the higher voltage... just because.. the energy density is too high, forcing them to stay put?
     
  13. davenn

    davenn Moderator

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    you are not too far off :)
    but the EM field is always moving in the direction of the charge.
    in a DC circuit the charge and EM field are moving in a single and same direction
    in an AC circuit, both the charge and the EM field are alternating back and forward

    from your link .....

    I agree with all that except one thing, yes the bold bit.
    The electrons/charge is flowing IN the conductor. The EM wave travels in the region outside and along the surface of the conductor
    You can think of the conductor as a waveguide. This is why with a coaxial cable ( or any other transmission line for that matter) the dielectric material surrounding the
    conductor is very important.
    it affects the Velocity Factor of the EM wave --- vacuum or air is best ... plastic, Teflon etc is worse
    Air/vacuum dielectric and the VF of the EM wave is close to the speed of light 96 - 98 % of such
    any material slows that and can come down as low as 66% ( give or take a bit)
    decreasing the VF increases the losses



    not sure what your definition of running backwards is in this context ?

    the negative side

    the diode presents a relatively low resistance when forward biased ... for an avg silicon diode it has a voltage drop of 0.7V across it


    if you really want to get into the theory ... get used to thinking of the flow is from negative to positive ... the flow of electrons


    an avg person can look at them either way and as long as you stick to the one way, you wont come to too much grief
    from a theory point of view it's better to use electron flow


    There are those that look at it from a flow of + ions point of view ( the flow of holes)
    but in reality, the positive ions don't move, they are part of the atomic lattice of the copper or other material. Its the outer several electrons of the atom that are mobile ( able to move)
    these are the valence electrons


    Dave
     
  14. Ratch

    Ratch

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    The electric field moves the charge carriers in a conductor, not the other way around. There is no energy transfer in a conductor unless the charge carriers move.

    You would do well to forget about analogies when determining how something works.

    A resistor heats and dissipates energy no matter what the current direction is. I said in my last post that energy transfers from the power supply to the components in the circuit, not the other way around. Why the big deal about the current direction?

    What does running backwards mean?

    If the current is present, the lamp will light no matter what the current direction.

    Are you asking how a junction diode works? I think you should learn how a circuit works first.

    Ditch the analogy and use real electrical principles.

    That is the mathematical convention provided the charge carriers are presumed to be positive and the conduction path is external to the power supply.

    There is no secret as to how ammeters and semiconductors are made. They are marked according to the mathematical convention. This means that applying a positive voltage to the plus terminal and a negative voltage to the minus terminal of the ammeter will move the needle from left to right, indicating a forward mathematical current. Since it is measuring negative charge carriers, the true direction is opposite the mathematical direction. Applying a positive voltage to the arrow of the diode will allow a forward mathematical current to exist, while the true current is opposite.

    Didn't I tell you that if you worry about the polarity of the charge carriers first, then you will be confused? Do the calculation using the mathematical convention first. Then, if you need to know the true direction, apply the polarity rule.

    The charge carriers move because they want to go the lower energy density (voltage). The positive ions cannot move because they are the fixed in place atoms of the conductor. They will not stay ions for long anyway because there are so many electrons present in metals that positive ions are drowned. There are no positive holes in metals, only in semiconductors.

    That reasoning is complete wrong.

    Ratch
     
  15. wbeaty

    wbeaty

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    Apr 30, 2010
    Heh, link to my website and I may suddenly appear.

    That's right. The energy in electric circuits is always wave-energy, EM energy. It can race along the columns of mobile charge within a conductor, where the charge is the "medium" for the propagating wave-energy. But it can also leap across the gap between transformer coils or capacitor plates. In general, in simple circuits, the energy travels 'instantly' along both halves of a circuit, along the two wires leading to a distant load. In a flashlight, the energy comes out of both battery terminals, races along the two connecting wires, and dives into the light bulb. At the same time, the movable charges within the conductors all move as a unit, turning either CW or CCW like a slow wheel or drive belt.

    The above may seem weird, but it's very common in non-electrical systems as well as electrical.

    For example, when you yank on a steel chain, each link in the chain moves towards you fairly slowly, while the mechanical energy flys out to the end of the chain at a few thousand KPH. The steel and the energy moved in opposite directions. Or, when you blow into a hose, the air in the hose moves slowly, but the pulse flys to the far end of the hose at roughly 1200KPH, the speed of sound. If you spin a flywheel by hand, mechanical energy comes out of your hand and spreads to fill the wheel instantly, even while the rim of the wheel turns slowly in a circle. Or the classic example: with a row of billiard balls, if you push on the first ball, the last ball in line moves almost instantly, since the energy traveled along the row of balls at the speed of sound (the speed of sound in wood.)

    Elsewhere in those articles I introduce the "wheel analogy" for the movable charges within electric circuits. The charges inside a simple electric circuit act like a single object, so a simple circuit is like a bicycle wheel. If you grab the rubber tire and force it to rotate, then energy flys out of your hand and all along the rubber, causing the whole wheel to move as a unit. Note that the energy flys both directions out of your hand, spreading outwards through the wheel both upstream and downstream. And, if you drag your thumb against any part of the moving wheel, your thumb pulls in energy from the entire wheel, converting it to frictional heat. The same thing happens in electric circuits, because the entire circuit is already full of movable charge, and the loop of charges behaves much like a solid ring-shaped object. If a charge-pump (battery) in the circuit should force the charges at one point to move, then the charges in the entire circuit must move too. Or, if a light bulb or other 'frictional' load is placed in the circuit, it extracts energy from the entire circuit as a whole. It's as if the charges inside the circle of wire were acting like a long, long piston. But it's a piston which curves around to meet itself in a closed loop.

    1) Yes and no, since the direction of charges depends on the type of conductor, and copper isn't the only conductor present.

    But more important, if a student asks about the real direction of flow, it might mean that they're using the incorrect "hollow pipes" concept, and wanting to follow the charges from the beginning. (There is no beginning, it's a wheel.) Or, they may be asking which component injects the charges into the "empty" wires. No component does this; the entire circuit is already full of movable electric charge. The circuit is made of movable electric charge. That's the physics definition of "conductor," after all. All of the "electricity pipes" came pre-filled with movable charge. The "wheel" was already there.

    Yes, circuits are based on electric current or Amperes. Current & amps is also called 'Conventional Current.' Electron flow is not electric current, because electric current is an abstract concept, a concept which intentionally conceals the charge speed, charge polarity, and charge quantity.

    Specifically:

    1. A dense cloud of charges moving slow can have the exact same Amperes as a sparse cloud moving fast.
    2. A cloud of positive charges moving left, passing through a cloud of negative charges moving right, gives a single Ampere reading, not two.
    3. Charges flowing from a thick wire into a thin wire will greatly increase speed, yet the amperes remains unchanged.

    And this means, when dealing with amperes...

    1. The number of charges is irrelevant
    2. The polarity and direction of charges is irrelevant
    3. The speed of charges is irrelevant.

    Instead, all the above is combined together to give a single number: "Electric current" or "Amperes," (otherwise known as Conventional Current, the thing measured by all ammeters.)

    Trouble is, usually we're asked to learn this stuff by osmosis, rather than having it explicitly explained. Also, we're supposed to learn the simplified abstract "Amperes" without first meeting up with the complicated real-world phenomena behind the curtain. For example, what would an electric circuit look like, if all of the hidden stuff could be made visible?

    2) The whole filament lights up at once. Similar question: if several thumbs were rubbing on a drive-belt, and the belt suddenly started up, would one thumb heat up first? No, but perhaps the thumbs on the ends of the series-of-thumbs would heat up first, stretching the belt and slightly delaying the wave of mechanical energy. Then the thumbs in the middle would heat up as their portion of the belt started moving too. Electric circuits do the same. To detect the turn-on, instead of a light bulb, use a string of diode-lasers with nanosecond turn-on time. When we close the switch, which laser turns on first? The one on the positive end, or the one on the negative? Neither. Probably both ends start at the same time ...but it depends on the location of the power switch!

    3) Diode in the circuit. The diode symbol shows the Amperes polarity for forward bias. A turned-on diode is a conductor, so electrical energy can propagate past it in either direction. But inside a PN semiconductor diode we have positive and negative carriers flowing in opposite directions. In one spot the opposite carriers fall together and annihilate, giving off heat and IR radiation, and leaving neutral crystal atoms. At another spot the positives and negatives are pulled out of the crystal atoms and forced to flow in opposite directions, almost like antimatter "pair production" in high-energy physics. Where this charge-sep occurs, heat-vibrations are absorbed, and that spot in the crystal grows cold.

    4) Diode design. There are semiconductor diodes, hot-filament vacuum diodes, gas-discharge diodes (mercury rectifiers,) and even crude electromagnet biased-coil diodes and electrolysis diodes from the late 1800s. All have the same symbol in a schematic, and all behave roughly the same. There is no "backwards" unless we reject the abstract idea called "Amperes" and drill down into the level of description called Component Physics. And in that case, the answer depends on the type of diode. Electrolytic diodes have simultaneous positive and negative flows in opposite directions the same conductor! This isn't too far from semiconductor diodes, with opposite carriers flowing together to vanish at the junction in tiny bursts of light.

    Yes, in lead-acid batteries the positive ions move to meet the incoming electrons. Positive ions in the electrolyte move to the metal plate, where they meet incoming electrons and cancel out. Actually, with acid-type batteries, these "positive ions" are H+ ions, hydrogen atoms with an electron missing. Which means, they're bare protons. Cool, eh? All acids fall under the class called "Proton Conductors." So, wouldn't the protons and electrons form hydrogen gas as they come together? Yep, that's where those H2 bubbles come from. (But in car batteries the dissolved sulfate gives up oxygen, forming water with the protons and incoming electrons. So, no bubbles under normal discharge conditions.)

    But that's actually answering a different question. Before the battery is connected, the electrolysis has removed electrons from the positive plate and also the positive terminal, exposing metal-protons in the solid crystal grid. These protons are immobile, while the ones in the acid are not.
     
    Last edited: Oct 6, 2015
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  16. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Welcome (back) to Electronics Point.
     
  17. GPG

    GPG

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    You would be surprised at how much similarity there is in the real world Hydraulics have circuit diagrams without which makes troubleshooting that much more difficult.Hoses have resistance valves often have pressure regulators and so on.
     
  18. Ratch

    Ratch

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    Similarity is a problem in learning one discipline by studying another. Many of the equations that define the operation of each field of study are the same, but some characteristics of each do not exist in the other. So things are almost the same but not quite when delving deeper into the operation of a circuit. Hydraulics is not the only analog to electronics. Masses springs, dashpots can be made into analogs of electrical circuits, too. My feeling is, why learn two or more fields of study when one is studying only one? I think analogs are good for narrow illustrative purposes, but not for learning how something works.

    Ratch
     
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  19. davenn

    davenn Moderator

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    totally agree :)


    Dave
     
  20. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Analogies are a bit like drinking. Up to a point they don't cause harm, but in excess they lead to negative outcomes.

    :D
     
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