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I hear plenty of people saying that voltage is just the potential for current to flow through, ergo, not actual flow.

However, if the potential is higher, the current CAN be higher.

So my question is, if the voltage is, say, 120v, does that mean current can't be more than 120 amps(falling within a potential)? If no, please elaborate on what "potential" exactly means within a circuit.

Saying "the difference between two points" doesn't really form a good understanding in my brain.

Voltage = current / resistance. If a circuit has no resistors, does that imply that the current is equivalent to the voltage(no resistance)?

If I'm right, please explain how. If I'm wrong, fill us all in here with what exactly "potential" means, and how it affects current, is related to power/energy, etc.

EXTRA: What I can't seem to understand is how this all works together. Someone tells me voltage is current divided by resistance, but if there's no resistance the current can be enormously powerful with almost no voltage? What?! No one seems to make sense of this.

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4 Answers 4

Voltage = current / resistance.

No, voltage is the product of current and resistance: voltage = current \$\times\$ resistance. Ohm's law:

$$v = i \cdot R $$

If a circuit has no resistors, does that imply that the current is equivalent to the voltage(no resistance)?

If there is no resistance in the (DC) circuit , \$R = 0 \Omega\$, and thus, \$v = 0V\$

$$v = i \cdot 0 = 0V $$

Someone tells me voltage is current divided by resistance,

Don't listen to them, they're wrong.

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Even if they're wrong, I don't think I can say you're making sense either. If there's no resistance, there's no current, is what you're saying? So I could stick a metal fork in an outlet, because there's no resistance, correct? With 0 volts, I should expect no shock. You are telling me no resistance = no electricity, so anything without a resistor has no electricity? –  user36503 Feb 1 at 22:43
    
@IaskQuestionsForaReas'n, I find it exceedingly hard to believe that you're serious. In fact, I suspect that you're deliberately being obtuse. –  Alfred Centauri Feb 1 at 22:53
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Voltage can be 0.1V and current can be 1000A. It's ohms law: -

I = \$\dfrac{V}{R}\$

If R is 0.001 ohms and V is 1V, I = 1000 amps

Think of a very thick wire carrying 1000 amps - it has virtually no resistance to worry about and there's virtually no voltage across it.

Think of a very thin wire carrying 1A - it may have 1 ohm resistance and the voltage across it will be 1V.

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That's pretty hard to fathom with the given stats. By those numbers, wouldn't I have been dead by attempting to run a copper wire between both ends of a 1.5v battery (there's no resistors) and touching the copper? The current would be very high, wouldn't it? What you're saying is that voltage, current, and resistance all fluctuate, but have no base connetion within a range with one another. That's confusing. –  user36503 Feb 1 at 20:49
    
Also, how would it make sense that something has resistance without resistors? Where does the resistance come from in a simple copper wire touching both ends of a battery? Why doesn't that kill you? EE doesn't make any sense(and I've spent years trying to learn it through books, courses). –  user36503 Feb 1 at 20:52
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@IaskQuestionsForaReas'n, Andy isn't saying anything like that at all. If you've genuinely been studying EE for years and you're still confused over these elementary concepts, it is unlikely that anyone here will be able to help you. –  Alfred Centauri Feb 1 at 20:59
    
Just because your power source can be exhausted before it happens doesn't mean it's not possible. For an infinitesimal period, even with a 1.5V battery, the behavior was as Andy described. Every power source will have its limitations, but that's independent from what was stated in the answer. Also, only superconductors have no resistance. everything else has. –  fceconel Feb 1 at 21:01
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I'm afraid none of you are making any light of this. All I get out of this is shifting answers that keep changing depending on context, and that don't add up. –  user36503 Feb 1 at 22:44
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Let's start with the word "potential". Voltage is referred to as potential difference for a few reasons. Voltage is really the potential to do work. It is always and can only be defined between two points because this "potential" must be with some reference to another point.

More formally, voltage is defined as the energy required to move charge from one point to the other. Phrased in another way, "the voltage between two points is one volt if it requires one joule of energy to move one coulomb of charge from one point to the other. (Circuit Analysis: Theory and Practice)" We always mention that voltage equals current times resistance [V = I X R] but if we want to define it, it may be better to say that it is the Energy (or work) per Coloumb, i.e. V = W/Q.

"I hear plenty of people saying that voltage is just the potential for current to flow through." Now this is where we talk about V = I x R (I will focus more on I = V/R, which is clearly the same thing stated a different way). The current in your circuit will just be a result of the potential difference (the voltage, i.e., the battery or source you provide) divided by the total resistance, including that of the wire and that of the load (let's say your light bulb).

To sum this all up, voltage is the potential to do electrical work (I could draw an analogy here with potential energy in mechanics but I left it out to avoid confusion).

EXTRA: Conductors are materials which charge (electrons, and thus current) can move through easily but they still do have some resistance. In reality, there is always resistance, even with a short circuit! Indeed, the resistance of the wire is what limits a short circuit to a finite amperage. Therefore, if you have a very small voltage, it's not going to do much for you.

I hope this helps.

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IAQ4AR,

The terminology we electronic types use can be pretty loose and illogical at times. This can really throw beginners for a loop!

The term "no resistance" used colloquially between electrical guys can mean two entirely different things.

First: It can literally mean "Zero Resistance", that is a resistor with a value of 0.00 Ohms, like a 1 inch piece of #8 copper wire. A zero ohm resistor is also known as a "short circuit". Connect a 0.00 Ohm resistor across any voltage source and the current will be infinite, or at least as high as that voltage source is capable of letting it go (typically many, many amps, and usually enough to cause something to smoke and burn).

Second: It can mean there is No Resistor. If hear this mistake often. Someone says there is "No Resistance" in the circuit when they mean there is No Resistor.

If there is nothing attached to a voltage source (i.e. "No Resistor" aka "No Resistance") the resistance of the load is INFINITE ( effectively, a billion gazillion Ohms). In this case the current will be 0.000000 because I=E/R. When you divide any value (in this case the terminal voltage of the voltage source) by a very large number (including "infinity") the result is 0.0 - a classic math principle.

HINT: After years of trying to explain Ohms Law to beginners with pen & paper, I finally came to the realization it can't be done. Now, I hook up a DC power supply, a resistor and two DMMs - one set for voltage the other for current. I vary the power supply between 3 or 4 voltage level, and run the math of the situation thru the basic Ohms Law equations. Next I substitute a few different resistor values and run the math again. Then, I leave my student to do it all by himself until he get's it right. At some point the proverbial "light bulb" goes off and he "gets it". It's much harder to understand on paper than it actually is in practice.

You can't learn to play baseball by drawing a picture of a baseball and a bat on a piece of paper. You need a ball, a bat and a glove, then you can start learning to play baseball.

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Bad analogy. If one couldn't understand it on paper (or visually), why should one magically understand it hands on? The concepts that drive the fundamental workings of electricity are always the same. If one doesn't get that, macro-scale rigging won't help either. I've connected circuits simple, like with lightbulbs and a resistor, but I couldn't tell you for the life of me how exactly that circuit is working in finer details outside of the basics. –  user36503 Feb 1 at 22:47
    
Try the "magic" to feel the magic! –  FiddyOhm Feb 2 at 13:40
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