Electric Circuits:  Basics of the voltage and current laws.
100 Comments


Suppose we take our circuit of a battery and a light bulb, and we make it slightly more complicated by adding a switch. When the switch opens, the charged particles are prevented from passing through. Particles with the same charge repel one another, and they therefore spread out throughout the wire. The events shown here all happen at the same time, and this is the result. For the light bulb to turn on, the switch must close, so as to create a complete path for the charged particles to flow around the loop. If we have several light bulbs, each light bulb can have its own individual switch. Or, we can have one switch which controls all the light bulbs. The number of charged particles that pass by each second is what we refer to as the current. The charged particles flow through the light bulb because the battery causes them to have a higher potential energy on one side of the light bulb than the other. This potential energy is what we refer to as voltage. If both sides of a light bulb are at the same voltage, then no current will pass through it. As the voltage across the light bulb increases, the amount of current through the light bulb also increases, and the light bulb produces more light. When a switch closes, it causes the two different parts of a circuit that it connects to be at the same voltage. If both sides of a light bulb are at the same voltage, then no current will pass through it. And if no current passes through a light bulb, then this means that both sides of the bulb are at the same voltage. A properly working battery ensures that the difference in voltage across it is always at a specific value. All points that are directly connected to each other through metal conductors and closed switches are at the same voltage. This means that if we have several light bulbs connected to a battery in parallel, the voltage across each light bulb is equal to the voltage that is produced by the battery. Since the voltage across the light bulb determines how much current passes through it, each of these light bulbs will have the same current pass through it as we had when we just had one light bulb connected to the battery. The total current drawn from the battery is the sum of all the currents drawn by each of the light bulbs. Now, let us consider a situation where we have several light bulbs connected in series. Since the total voltage across the group of light bulbs is at the specific value set by the battery, the drop in voltage across each light bulb is only a fraction of this. Since the current that passes through each light bulb depends on the voltage across it, this smaller voltage across each of the light bulbs means that a smaller current will flow through them. This means that the lights will not be as bright. Because the light bulbs are connected in series, this means that the current passing through each of them is the same. The amount of current entering always has to be equal to the amount of current exiting. This is what we refer to as Kirchhoff’s Current Law. This is accompanied by another law, called Kirchhoff’s Voltage Law, which states that as we travel around a loop, the amount of voltage increases that we experience must be exactly equal to the amount of voltage drops that we experience. The use of these two laws together allows to analyze all electric circuits, no matter how complex they become. Much more detailed information about voltage, current, and electric circuits is available in the other videos on this channel.

100 thoughts on “Electric Circuits: Basics of the voltage and current laws.

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  2. Fantastic visual illustrations. I have one question. In this video you show what looks like a Duracell battery where the positive end is copper coloured. Therefore, it looks like the positive end is pushing negative electrons around a circuit. Shouldn't we turn the battery around?

  3. Definitely helping me understand more! Still having just a bit of trouble with this, especailly when it came to Kirchoff's Voltage Law. Will give in a rewatch in a little while just to let it sit in my brain, and then hopefully revisiting that will help solidify it more.

  4. Hi, unvaluable content as always, could you please tell me the the name of the music in the background?

  5. I Got it now, little red balls flow thru my house causing the lights to come on and off. I knew there was a logical answer.

  6. The problem here is the the flow is reversed and they show it flowing constantly. The electron flow will flow from negative to positive and stop. It shows the movement through the battery which wouldn't be correct. Once the electron moves from the negative to positive in the battery eventually balancing out the atomic structure on both poles causing a dead battery and no electron flow.

  7. Why are you showing the current cycling through the battery as though it's perpetual?

    I know it's probably obvious that it doesn't work that way but seeing it makes the whole thing seem questionable when this is a nice depiction otherwise.

    Maybe, instead of having the current ride up the battery, you could just have the current appear out of the top and disappear at the bottom.

  8. Hi! may I use this video, as is with credits and all to explain these concepts to my students of firstyear engineering in a college in India?

  9. Keep in mind.

    Their example makes it appear as if a "wire" is coming from the battery terminal.

    But a real wire has both a "hot" and "neutral" line built into it.

    Therefore, if you wire lights with a hot and neutral wire in and a hot and neutral wire out, you are wiring the lights "in parallel" even though it seems as if there is one "wire" going to each light in series.

  10. Your electrons flow the wrong way, stop using conventional way, use current way of electrons flowing, you confuse people 🤦‍♂️

  11. Can someone explain me why the voltage across the light bulb determines how much current passes through it ?

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  13. The current is flowing the wrong way!!! Additionally, the positive charge attracts free electrons, it does not repel them… turn the battery upside down to fix things 😉

  14. There was a mislead in the animation of particle flow in the video. Particles (electrons) do not move from positive to negative pole, but rather the reverse.

  15. Wow…! This is such garbage and the worst part is it's actually accepted by complete fools. Eugene you really are one pathetic fool! Do you ever stop to think before you make this garbage? You really are helping ruin a lot of minds with this electrons traveling through wires. LOL you clearly are not an electrical theorist. What high school physics book are you referencing all of your nonsense from question mark you really should wake up to reality you absolute waste of time.

  16. Intuitive video but electric current is the amount of charge not the no. of charged particles passing through a cross section per unit time.

  17. No question it explains Voltage and Current well.

    But I miss the clear statement that electrons do not move from point A to B.
    Instant they only move in the orbit of the next atom and there force an electron out and that moves to the next atom and do the same etc.

    This would be nice at 3:50, to make it clear why the electrons take the long way at the same voltage level.
    And that means the process between 0:12 and 0:44 does happen, if there is no electron who push all electrons stay in their own orbit.

  18. Great Graphics. Only issue is it shows current flowing in the external circuit from positive to negative. Current in a DC circuit flows from negative to positive. Thanks for a great demonstration

  19. Why does the animation seem to show a charged particle (electron) waiting on the supply side of an open switch when there are closed switches in the circuit? Electrons would flow to and through the connected loads via the closed switches (path of least resistance). Think of it as a route diversion on your journey home; you're not going to wait at a barrier for a closed road to open up. You will go the other route in order to get home.

  20. This is one of the best explanations about how current move. The electron is naturally negative charge in static state of any conductor. And you pull this electron by a positive charged power which are the protons.

  21. 4:06 Isn't this animation wrong though? Because electrons always takes the shortest path. The side with the longer path would be the one with no electron flow rather than the side with the light bulb.

  22. So, is it the voltage or the current generating light? Why higher voltage will make the light bulb brighter and even burned out? Why door knob voltage doesn't kill you even it's known to reach 2000 volts? What is heat and what is light? What is the difference between the flow of electricity and the flow of fluid like water in the pipe?

  23. These are quite well done. I feel one of the demonstrations could have used a brief point about resistance. The one with the small square detour and switch that bypasses the light build. Knowing that the light bulb has a slight resistance helps to explain why the current takes the long way around when the switch is closed. Minor point really.

  24. Isn't an electron a "Quanta" of light energy embedded in a "Nullitron" (if you will) and this in turn produces the effect that we know and understand as an ATOM with an associated charge cloud differential and angular momentum (SPIN)….???????????
    If this is the case then why are we shown electrons as ball bearings??????????

  25. Sir, Every force has equal and opposite force, in an circuit connected by an battery, the electron from anode of battery, PUSHES electron near by(in the conductor) , that near by electron pushes it's near by electron, this chain of pushing, ENDS at CATHODE , while PUSHING, the electron from anode will DECELERATE. But in formula of drift velocity, this deceleration is not included….. WHY? (if I am wrong correct me SIR)

  26. Wonderful animation of a perfect scenario An animation of an imperfect circuit would help as well to show loose connections and how that extra resistance can make things troublesome

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