What is Open circuit: Definition and 60 Discussions

Open-circuit voltage (abbreviated as OCV or VOC ) is the difference of electrical potential between two terminals of a device when disconnected from any circuit. There is no external load connected. No external electric current flows between the terminals. Alternatively, the open-circuit voltage may be thought of as the voltage that must be applied to a solar cell or a battery to stop the current. It is sometimes given the symbol Voc. In network analysis this voltage is also known as the Thévenin voltage.
The open-circuit voltages of batteries and solar cells are often quoted under particular conditions (state-of-charge, illumination, temperature, etc.).
The potential difference mentioned for batteries and cells is usually the open-circuit voltage. The open-circuit voltage is also known as the electromotive force (emf), which is the maximum potential difference when there is no current and the circuit is not closed.
The opposite of an open circuit is a "short circuit".
To calculate the open-circuit voltage, one can use a method similar to that below.

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  1. L

    Current flowing in an open circuit

    1. Consider this diagram. Does the bulb light up? The equation I=V/R tells me no, but if there is a potential difference between the two points, surely current will flow and the bulb will light? As there is nowhere for the electrons to go, I assume it will only light for a very short period of...
  2. A

    Engineering Short vs Open Circuit: Is That Correct?

    For the first circuit, Req = ZL + ZC = -j/(w*C) + j*w*L = 0 for short circuit, so w = 0? For the open circuit case, -j/(w*C) + j*w*L = infinity, so w = infinity? Is that correct?
  3. Salmone

    I Can current flow in an open circuit?

    I have two related but separated questions: 1. If I have an open circuit connected to a battery, let's say an alkaline battery connected to a straight wire and nothing more, once I connect the battery to this wire there will be for a short time a current in the wire? Since in the battery due to...
  4. F

    Simulate open circuit and short circuit in MATLAB

    Here's my attempt: The results I got are close to the required answer, but there is a question telling: I tried to solve it, but Isc and Vt (in open circuit) are decreasing with the increase of the field current , so I didn't get the right answer. Could someone let me know where is my...
  5. JamesBennettBeta

    Finding the Open Circuit Voltage

    Problem Statement: While KLM points remain connected, the connection between points XY is removed. Calculate the potential difference between points XY in this situation. Relevant Equations: V=IR, KVL
  6. M

    Does Mutual Inductance Affect Voltage in an Open Circuit?

    Hi, so my question is basically: Does the mutual inductance from coil 1 show up in the voltage of coil 2 even if coil 2 is an open circuit? I would think that the answer is yes, as the Mutual inductance depends on the current passing through coil 1? However, the answer scheme seems to ignore...
  7. cianfa72

    Galvanic cell - open circuit voltage and EMF

    Hi, having not a deep knowledge of electrochemistry I've some doubts about processes involved in a galvanic cell. Take for instance a Zn/Cu Daniell cell for which E0cell is 1,10V. That means emf for it is 1,10V. Starting to read from how battery works I had a first understanding of how...
  8. H

    Open circuit voltage of an old battery

    Why the voltage of an exhausted battery, in open circuit state, is almost identical with that of new battery? The internal resistance of an exhausted battery is very large and so, the large amount of energy consumed by the source (for overcoming the electric filed in the battery) would waste in...
  9. A

    Why isn't a capacitor an open circuit?

    I understand the basics of how capacitors work. If you hook one up to a power source, negative charge will build up on one plate, and positive charge will build up on the other plate. As the charges build up, an electric field forms between the plates and a potential difference is established...
  10. H

    How to choose a fan for open circuit wind tunnel?

    Hi all, I am trying to design a open circuit wind tunnel, and I've got to the point where a fan should be selected. However, I am not familiar with fans at all, so I am wondering if you could help me! My understanding is that the fan selection process is quite similar to the pump selection...
  11. ltnghia1304

    How to find the open circuit voltage?

    Homework Statement How can we find the open circuit voltage of this one: Thank you Homework EquationsThe Attempt at a Solution
  12. C

    Open Circuit Termination for Waveguides in High Frequency Labs

    Hi everyone, I am trying to understand that why do we use open circuit terminator for wave guides or any RF element such as coupler and etc. I know if we just leave it open, it does not work as open circuit. But why?
  13. Biker

    Voltmeter: Open circuit

    Homework Statement What is the reading on voltmeter 1 and 2 when K is open? http://blob:http://imgur.com/2d84e21a-63e2-4021-b4d9-e37231816d38 [Broken] Homework Equations There isn't any. The Attempt at a Solution Okay so I have two answers for ##V_1## and ##V_2##: What I am thinking is that...
  14. Marcin H

    Engineering Open Circuit Voltage and Short Circuit Voltage

    Homework Statement Homework Equations V=IR Current Loop method, KCL, Node Voltage The Attempt at a Solution I am struggling with this problem because I haven't seen a circuit like this before. I think I found the Voc correctly (4V) but I am stuck with finding the short circuit current. I...
  15. J

    Engineering Determine the open circuit voltage for VL

    Homework Statement See image attached Homework Equations Voltage divider law? Ohms law? The Attempt at a Solution I am unsure on how to treat the problem since I have only learned how to find information within parallel circuits and series circuits. I tried to use the voltage divider law...
  16. GauravU

    Open circuit test of 3 phase transformer in Ansys Maxwell

    Hi all, I am designing a three phase 11000/433 Volts Delta/Star 50 Hertz transformer in Ansys Maxwell. It has 792 turns in 6 layers on HV side (132 turns per layer) and 18 turns in 2 layers (9 turns per layer). The resistance as I have calculated is 0.1325 ohms per phase of HV winding and 5.57...
  17. S

    Short circuit current and Open circuit voltage -- Illumination

    Homework Statement I'm trying to understand the dependence of short circuit current and open circuit voltage on illumination. Short-circuit current is due to the generation and collection of light-generated carriers -- so does that mean the short circuit current is linearly dependent on...
  18. P

    How to find equivalent circuits

    Hi, I need to learn how to find equivalent circuits using what my textbook calls open circuit and short circuit methods. Thank you all for you support
  19. J

    Charge transfer between two capacitors in an open circuit

    Hello everyone, I have drawn a picture of my confusion, I think it says it all: Now to add some text: so we charge two capacitors C1 and C2 to a voltage V. Now we have two charged capacitors. We now connect -Q1 to +Q2 and nothing else (the other two legs are floating). From my basic...
  20. T

    Open circuit armature voltage of dc machine?

    Homework Statement The book says that "the induced voltage E_a can be found by measuring the open circuit voltage at the armature terminals" Homework EquationsThe Attempt at a Solution But isn't there a voltage drop across the resistor so that they can't be equal? or is this ignored
  21. X

    If current doesn't flow in an open circuit, how are capacitors charged?

    When answering a related question on physics forum, I found something I seemed to be confused about: Suppose we have a battery connected in series to a capacitor with no charge. A capacitor with no charge on it acts like an open circuit. I know what happens next: the battery charges the...
  22. M

    Confused about short circuit and open circuit

    i know that short circuit is when current is max while resistance is zero and open circuit is when resistance is infinite and current is zero, but in terms of voltage, if i have a part of circuit and i want to know whether it is short or open circuit and i only know : the voltage and if the...
  23. M

    Fuel cell open circuit voltage and pressure of reactants

    Hello, I have some questions regarding the nernst equation at open circuit voltage. We know E(OCV) = E0+ ln (PH2*PO2^0.5 / PH2O) I have some trouble with this: If I have dry gas (both for O2 and H2), and my circuit is open at 25°C and 1 atm I have no water in the circuit so what become the...
  24. I

    Problem with open circuit

    Homework Statement Find the value of v1, v2, vab, vbc, vca. See picture Homework Equations Kirchoff's Law The Attempt at a Solution Is it true that both current through 3 and 4 ohm resistors are zero? The way I think of this is if they aren't zero, there would be charge building up at a...
  25. T

    Open circuit short circuit (test) TX flux effect

    Hi, It's been a while but from what I remember when you short circuit a transformer, electrically it's like you've series'd up the coils and shorted the magnetisation branch. And when you open circuit a side of the TX it is like the current flows through a side then through the magnetisation...
  26. G

    Engineering How can voltage flow in a open circuit

    Homework Statement Hi Guys, I am wondering how voltage can flow in an open circuit as I = 0 so surely V=IR; V = 0*R so V = 0 I know it does as when a capacitor is fully charged no current flows yet there is a voltage. I'm about confused thanks! Homework Equations V = IR The Attempt at a...
  27. L

    Electric power = I2*R= (0)2*infinity = can be any thing for open circuit?

    In an open circuit resistance is infinity and therefore current is zero.(voltage 220V) power=iv=0*220=0 watt power=I2*R=(0)2*infinity=can be any thing (V=IR) so,is power consumed zero or any thing?
  28. I

    What does Open Circuit Voltage mean?

    I have a multimeter and for the "ohmeter section" for resistance it goes from a range of ~ 200 Ohms to 2000 kilo-ohms and then says also... Max. Open Circuit Voltage: about 3V Overvoltage protection: 250V AC Thank you in advance
  29. C

    Does a battery becomes open circuit when it's full? capacitors does?

    When a batter is charging, let's say 3V battery.. when it's full, does it stops there or continues to take in charge? Like for example, capacitors charges up, until it reaches the voltage which was charging it, when both becomes equal, the cap becomes open circuit.. i wonder if batteries also do...
  30. C

    Engineering Transformers open circuit and short circuit test confusion

    Homework Statement A 50 KVA,6360 V/230 V transformer is tested on open and short-circuit to obtain its efficiency,the results being as follows: O.C.: Primary Voltage-6360 V, Primary Current-1 A, Power Input - 2 kW S.C: Voltage across primary winding-180 V Current in secondary...
  31. K

    Capacitors , why cant series combination be used in an open circuit?

    Capacitors , why can't series combination be used in an open circuit?? they say we cannot apply series combination formula for the capacitors in an open circuit,,,but why?? why can't we find the equivalent capacitance in an open circuit?
  32. Entanglement

    Electric Current in an open circuit

    I'm still a beginner at Electricity and electromagnetism, I'm wondering If we connect a wire to a positive terminal ONLY , why won't the electrons flow to the positive terminal of the cell as electrons are negatively charged, I have been days thinking about it and I need a clear convincing...
  33. F

    Solar cell open circuit voltage and bandgap

    Hello Forum, if we take a silicon solar cell, the open circuit voltage is about 0.5V. the current increases as the solar cell area and illumination increases. But the 0.5 V output voltage does not change as the area and illumination level vary...Why? It must have something to do with...
  34. P

    Engineering Synchronous Machines - Open Circuit and Short Circuit Tests

    This was a theoretical / rhetorical question posed by the professor during class. He hinted that this will be on the next quiz. I think I know the answer, but can you guys verify it for me? Homework Statement Why do we not perform the Open Circuit Test and Short Circuit Test one after...
  35. T

    Engineering How to find voltage in an open circuit

    Homework Statement Hi guys, attached is a photo of the circuit. Apologies for the bad drawing, but paint is hard :P What I am wondering is, how do you find the voltage of the open circuit with circuits like these? I have used Thevenin and Norton equivalent circuits before, but the...
  36. P

    Open circuit with capacitor

    The problem asks to find the steady state voltage across the capacitor. i attached the circuit (sorry for the poorly drawn and yes, that open part of the branch is supposed to be there) This is a multiple choice question where the answers are: a) 0V b) V_dc/2 c) V_dc/3 d) V_dc e) 2*V_dc...
  37. M

    Open Circuit Problem with Logic Gates

    I wonder how can I make the logic gate read 0V when it is open? For instance, the AND logic gate. If one of its input pin has 5V supply, and the other don't have, the output signal given to me is 5V. How can I make it 0V? Well, theoretically, it should be 0V, but in reality, it appears that...
  38. Y

    Engineering AC circuit with dependant current and voltage source and open circuit element

    I've been given the following problem (attached), not sure how to tackle this one, do I use mesh/node analysis and super node analysis, or can I find the v in the loop with the dependant voltage source then use that as the supply to the second and third loops? Not sure, any help would be...
  39. S

    Voltage in an open circuit.

    Hi guys, I have recently started to think about basic electronics and realized that I don't know electricity theory at all cause I couldn't answer a few questions asked by my friend. Imagine an open circuit(forum_pic) Wiill there be any current at all. I...
  40. J

    Role of a voltmeter in an initially open circuit

    Hi! Could someone briefly explain the following scenario to me please :) If an open circuit (with the 2 ends named X and Y) hung on a string is swung through an into page magnetic field, what would the emf be? How would that change if you are asked about the voltage 'measured' between X and Y...
  41. R

    Voltage across an open circuit

    The potential difference between the two grounds in this circuit can be determined with the equation AB = X + Z where z is the voltage source and x is the node at the top of the circuit, and AB is the potential difference between the two grounds. Could someone please explain to me...
  42. Y

    Electric potential in an open circuit

    Hi, I was wondering, if a circuit is open, would capacitors still have a potential difference ? If there is no potential difference, can we say its potential is 0 then obtain a charge equal to 0 for the capacitor's charge ?
  43. T

    Solenoid in open circuit and with glavanometer attached

    1.A student performs an expierment on a soenoid. The solenoid is open circuit in the first instance, the studet then pushes a magnet into one end with a constant force. the second instance, the solenoid is connected to a galvanometer. Using the concept of energy conversion, relate and explain...
  44. J

    Voltage across open circuit (very basic question)

    Vs to R1 to R2 to R3 to ground If there is an opening in the circuit between R1 and R2, why is it that when I measure the voltage between R1 and R2, it equates to the voltage source voltage? Why does the resistor not matter? If the circuit is normal without any opening, what will I get...
  45. Y

    Voltate, Resistance of open circuit

    There is a open circuit like below figure A---------R(10ohm)--------V(10V)-------------B The Voltage between A and B is 10V. The resister do not affect in this circuit. This is what I have learned. But I do not understand why the resistance do not affect to the voltage value. Please...
  46. N

    Current in an open circuit

    I've always wondered why is it possible for charge to flow in an open circuit, e.g., when a terminal is connected to a grounded pole, a large metal chassis, or say a water pipe. I've assumed that it's because there is a positive potential difference between where the charge is and the large...
  47. F

    Open circuit voltage & EMF help

    Any help appreciated with these! Homework Statement 1. A battery is made up from a series combination of six 1.2 volt nickel cadmium cells supplying a 10ohm load- a) What is the open circuit voltage? b) Ignoring internal resistance, what is the current flowing in each cell? 2. The nickel...
  48. M

    AC voltage source in an open circuit

    Please see the attached illustration. This is clearly an open circuit. The voltage source is producing a voltage at some amplitude and frequency. If one were to measure with an oscilloscope the potential difference at the point where the mouse pointer is with respect to the ground, what would...
  49. N

    Engineering Understanding Transformer Power Measurements with Open Circuit Experiment

    http://i44.tinypic.com/142zgg5.jpg they say that we can measure aM and R_c they say that in a good transformer the power waisted on R_1 is much smaller then on R_c then we can neglect the power on R_c so the power measured on the power meter will be the power on R_c...