Suppose we use a 9V battery.  Then the voltage between these two terminals is 9V. In other words, it would take 9 J of energy to move +1C of charge from the (+) to the (-) terminal by the electric field established by the battery.  So exactly how can electrical components "reduce" this voltage?  How can we say that the potential difference between a resistor connected to a battery is 9V?  This would obviously imply that the voltage would have to "move" in the circuit, such that right before the resistor, the potential is 9 V.  Then after the current passes the resistor, the potential at this point immediately after the resistor, it is somehow 0 V.  But this is wrong by definition, because it is +9V at the + terminal of the battery, and 0V at the - terminal of the battery.    I am confused?
23496
I'm having trouble conceptualizing why the voltage drop between two points of an ideal wire (i.e. no resistance) is $0~V$. Using Ohm's Law, the equation is such:  $$ V = IR \\ V = I(0~\Omega) \\ V = 0$$  However, conceptually I can't see how there is no change in energy between these two points.  It is my understanding that the electrical field of this circuit produces a force running counterclockwise and parallel to the wire which acts continuously on the electrons as they move through the wire. As such, I expect there to be a change in energy equal to the work.  Voltage drop is the difference in electric potential energy per coulomb, so it should be greater than $0~V$:  $$ \Delta V = \frac{\Delta J}C \\ \Delta J &gt; 0 \\ \therefore \Delta V &gt; 0 $$  For example, suppose I have a simple circuit consisting of a $9~V$ battery in series with a $3~k\Omega$ resistor:    If the length from point 4 to point 3 is $5~m$, I would expect the following:  $$ W = F \cdot d \\ W = \Delta E \\ F &gt; 0 \\ d = 5 &gt; 0 \\ \therefore W &gt; 0 \\ \therefore \Delta E &gt; 0$$  Since work is positive for any given charge, the change in energy for any given charge is positive -- therefore the voltage drop must be positive. Yet, according to Ohm's Law it is $0~V$ since the wire has negligible resistance.  Where is the fault in my logic?
119375
I am an electronics student, and I was set some homework online. I am not having trouble with the question itself but the theory. It says that the current through the resistor is the same as the maximun current that the diodes can safely handle, but as you can see, there are (\$V_{out}\$) volts being dissipating to the right, and a minimum required current going through the diode to maintain consistent voltage.  The thing is, how could the current through the resistor be the same as the current through the diode, as \$Voltage=J/C\$, or, joules per coulomb, so that means there must be some energy carried by the coulombs, and ultimately, some electrons. But then this is contradictory, wouldn't the current going through the resistor be the total current, the current dissipated to the right and current through the zenor? Or... is it that there isn't, then, any current passing at \$V_{out}\$? and it doesn't represent voltage being dissipated? I cant wrap my ahead around it...
30238
Note: I am very new to the more advanced side of electricity. I do not have a firm grasp on the exact mechanics.  Lets say I have an example circuit:  5V Power Supply -&gt; LED -&gt; Resistor -&gt; Ground  Now the LED is receiving 20ma and 5V. If I were to switch the LED and the resistor however, the LED should receive less voltage but the same current, so wouldn't it be dimmer? Or would it receive the same voltage?  I've looked at these two threads and their answer doesn't help.
19047
I am taking my first steps into learning about electronics as a hobbyist and I am struggling to understand something about resistance.  I have read about Ohm's law and it seems fairly straightforward so I set up a simple circuit on .    This circuit consists of a 9V battery and a single resistor (10 Ohms) with its leads connect directly to the 9V battery.          &ndash; Schematic created using   When I place the probes of their simulated voltmeter across the leads of the resistor, it reads 7.83V.  I can't make any permutation of Ohm's law produce that result.  What would be the expected voltage across the resistor?  Based on other posts on this site, I would expect the voltage to be 9V.  I don't know how that simulator (123D) calculates its values or how it simulates the circuit.  I am sure that I am missing something fundamental but so far I haven't figured out what.  Is the 123D circuit simulator right?  Should there be only 7.83V across that resistor?  I set up a similar circuit (using CircuitLab) and it seemed to show that the voltage would be 9V.  So I am confused.  Is this just an inaccuracy of the 123D's simulator?  Can someone help me to clear the fog?
87857
I've learn some electronic knowledge at school and so confused by some questions.  Q1. IS it possible a flow of electricity without an electric field?  Q2. I've learn that moving of particle with electric charge in electric field makes potential difference. Then, let's suppose no resistance in wire. IF Q1 is true, wire with a flow of electricity makes an electric field, and in the electric field, an electron moves. Then potential difference must exist. But when measured, there is no potential difference. ( I learn there is ESR in battery, but I wonder whether moving of electron dosen't make any potential difference or not.)  Sorry for my bad English, but I hope someone could help me to find answer.
109978
How is it possible that in scenario 1 resistor R1 converts 5V of energy to heat and in scenario 2 the same resistor R1 converts 2.5V of energy to heat?  The resistor R1 in both scenarios are exacly the same, I don't seem to grasp what happens on the physical level to the electrons how they "know" when to dump all their energy at once in resistor R1 in scenario 1 or to divide the energy they have proportionally over the resistors R1 and R2 in scenario 2.  I have read an explenation , but it's still not clear. How is it possible that the voltage is different at point A going through the same amount of resistance? I would expect a linear relation between voltage and resistance.  Could someone explain what physically happens that causes this?         &ndash; Schematic created using   Edit  Is my understanding right? According to   The resistance drops liniar along the path.  In scenario 1 at the start of R1 the resistance the current encounters is 100\$\Omega\$ and at the end of R1 it encounters 0\$\Omega\$.  In scenario 2 at the start of R1 the resistance the current encounters is 200\$\Omega\$ and at the end of R1 it encounters 100\$\Omega\$.  If this is true, why does point A in scenario 2 have more volt left if it has encountered a higher resistance of 200\$\Omega\$ at the beginning opposed to scenario 1 where it encountered 100\$\Omega\$ at the beginning?
87275
I have read from some book that: "The voltage quantity symbol V sometimes has subscripts to designate the two points to which the voltage corresponds. If the letter a designates one point and b the other, and if W joules of work are required to move Q coulombs from point b to a then, \$V_{ab}=\frac{W}{Q}\$. Note that the first subscript is the point to which the charge is moved"   While Wikipedia () says: "\$V_{CB}\$ means the "\$V\$" from \$C\$ to \$B\$."  Can you help me with the true meaning of the first subscript?
70742
I am beginning of learn electricity so sorry if my questions are confusing or does not make sense. My question is specifically about how voltage (which I guess is due to separation of uneven charges) is constantly maintained in a battery. My knowledge of battery comes from chemistry and there examples of battery were not as complicated as those found in physics. Like in chemistry we learned of how electrons traveled one one electrode to another another and when the charges are evened the battery then dies. But in physics I am reading of examples when the battery constantly maintains the voltage and charges keep on traveling the circuit even when they reach the other terminal. Can anyone explain how this is happening? I guess I don't understand how batteries work completely.
41841
Consider two circuits containing a battery, bulb, switch and conducting wires but of length 1 meter in one case and 1000KM in other. When switched on at the same time both the bulbs glow instantaneously. I think it is because, electric filed travels from positive terminal of battery to negative terminal through wire almost instantaneously.  My question is there any speed for this electric field? If yes, what is it? By any modification in this circuit is it possible to induce any delay in glowing the bulb?
116336
An electric potential difference is created when two charges are separated. In a capacitor, there is a clear accumulation of opposite charges on the two separated plates, therefore work has to be done in moving an unit charge from one plate to another, against the electric field.   But, , a potential difference is created in a resistor due to the heat produced by the collision and increased lattice vibrations. So there is an energy loss across the resistor, yes, but how does this energy loss due to heat create an electric potential difference. In other words, do electrons accumulate on one or both sides of the resistor? If not, why should we do electric work in moving from one end of the resistor to another. If the difference in energy is not due to electric work, then that's not electric potential, is it?
109897
I had the following question on a quiz recently:     A capacitor consisting of two parallel plates, separated by a distance $d$, is connected to a battery of EMF ε. What happens if the separation is doubled while the battery remains connected?    The correct answer was "The electric charge on the plates is halved." However, we were previously given a question in which a circuit consists of a capacitor of 6 μF and a resistor of 300,000 Ω connected to a battery, and the separation between the plates of the capacitor is quadrupled. However, in this circumstance, the charge on the capacitor immediately after the plates are separated remains the same, and the potential difference across the capacitor increases.   I am confused as to why these questions have different answers to them, despite having an extremely similar setup. My best guess is that the circuit in the second question also has a resistor, but I am not sure, and help would be greatly appreciated.
118443
I was just wondering what happens in a circuit in terms of different types of energy transformations. If you apply a voltage to a circuit then electrons start moving (very slowly). Since the electrons want to flow to the positive terminal they will have electrical potential. But the electrons are also now moving once the voltage is applied as there is a current so would they have kinetic energy as well?   Some information I have found online says that electrons collide with atoms in a bulb and this is why the filament heats up. But this would imply that kinetic energy is being transformed into heat and this can't be correct because surely any change in kinetic energy would alter the current flowing? Also, in a series circuit, if you measure the potential difference between any 2 points after all of the loads then you always get zero. I was just wondering why it is zero because don't the electrons keep moving even after passing through all the load in order to get back to the power source so surely they cannot do this without some form of energy?
102360
We know that the electric field inside resistor produced by battery is the actual thing that pushes the electrons in it to move and thus producing some current. We also know that strength of electric field can be described by the electric flux which is the total amount of fields passing through an area. That flux when combined(multiplied) with charge of electron gives the amount of force on it. Now comes our two resistors R1 and R2. Assuming a number of field lines coming out of a terminal going towards another terminal through these resistors, the field lines should get divided into the resistances R1 and R2. Therefore giving a reduced flux through each resistor than in a series. Which will then give a lower voltage for both resistors. Wasn't the electric fields strength divided across resistors in parallel? What is the main cause of voltage? How electrons get a force to produce current even when the wire is very long in? I think it is better to understand with reality than analogy. Please don't give misleading pictures
104689
Electric potential is related to Electric Field by negative integral of Field with distance.If charges move away from the positive terminal (Assuming conventional flow) why is there no drop in electric potential even though the charges are moving in the direction of electric field?  Some of the answers I read for the similar question said that the electrons in wires rearrange themselves in a way to make the electric field uniform in the wire.However,this doesn’t explain the absence of potential drop in the wires (due to electric field) since the field is still there.
39717
Why does voltage remains same over parallel circuit. If a resistor is connected in the circuit some of the charge should be transformed into heat and make a lack of charge after the resistor (in my sense). So, what's the reason in it?
86821
As I understand, the different voltage between two object is caused by the total different charged between two object. Thus, the higher extra electron between two opposite charged object, the higher voltage between them, isn't it? So if i have two battery or capacitor connect in parallel, the negative connect to negative, the positive connect to the positive. Caused the charge from each plate to be double. So that's as my expected, it must be double voltage, but ironically why it's out of my expected and the reality is vice-versa?
25748
Ohm is defined as      "a resistance between two points of a conductor when a constant potential difference of 1.0 volt, applied to these points, produces in the conductor a current of 1.0 ampere, the conductor not being the seat of any electromotive force"    according to  wikipedia page. However, I still don't understand what exactly is resistance and ohm. Does resistance decrease the amount of electrons passing through a conductor per unit time or does it decrease the energy that a single electron carries or none of them? I know what Ohm law is and I also know the mathematical background of resistance but I can not understand the logic behind it.   For example, when we talk about a conductor that should be insulated by an electrical insulator we have to know how many ohms that is needed to determine the size of the insulator for a good insulation. But I would like to know how it is determined. Thus, I would be pleased if someone could explain the logical background of resistance and ohm. Thanks.