What is Voltage: Definition and 1000 Discussions

Voltage, electric potential difference, electromotive force (emf), electric pressure or electric tension is the difference in electric potential between two points, which (in a static electric field) is defined as the work needed per unit of charge to move a test charge between the two points. In the International System of Units, the derived unit for voltage (potential difference) is named volt. In SI units, work per unit charge is expressed as joules per coulomb, where 1 volt = 1 joule (of work) per 1 coulomb (of charge). The old SI definition for volt used power and current; starting in 1990, the quantum Hall and Josephson effect were used, and recently (2019) fundamental physical constants have been introduced for the definition of all SI units and derived units. Voltage or electric potential difference is denoted symbolically by ∆V, simplified V, or U, for instance in the context of Ohm's or Kirchhoff's circuit laws.
Electric potential differences between points can be caused physically by electric charge build up or imbalance (eg. well known "static" and electronic capacitor) also by electric current through a magnetic field, and by time-varying magnetic fields (eg. dynamo or generator), or some combination of these three. Additionally on a macroscopic scale potential difference can be caused by electrochemical processes (cells and batteries) and pressure induced piezoelectric effect and heat induced emf across metal junctions. These latter processes at microscopic level have the physical origins previously mentioned. A voltmeter can be used to measure the voltage (or potential difference) between two points in a system; often a common reference potential such as the ground of the system is used as one of the points. A voltage may represent either a source of energy (electromotive force) or lost, used, or stored energy (potential drop).

View More On Wikipedia.org
Recent contents Top users
  1. Sid55

    Schottky diode with the correct voltage and current rating

    Non-isolated boost converter Input Voltage: DC8.5V to 50V Output Voltage: DC10V to 60V Max. Ouput Current: 12A Frequency: 150KHz
  2. R

    Finding Equivalent Resistance, Current, and Voltage across a resistor

  3. D

    Planning to measure voltage (back EMF) caused by opening a switch in series with an inductor

    i am planning to measure the back emf produced by inductor when you open a switch. i know it is very hard to predict the voltage. but is there any way to narrow the possibilities?
  4. D

    What happens if I apply a voltage to human flesh?

    if i apply a voltage to human flesh, human flesh would be at the full voltage? because i performed an experiment. i connect one end of a wire to the the palm of my hand. i connect the other end to a battery. i connect the first battery to a second battery. i connect the second battery to a...
  5. M

    Engineering Calculating Voltage Drop Across Non-Ideal Diodes

    So I have this circuit up above and I need to find the voltages across each of the diodes. The only info given is that they are identical silicon diodes at T = 300K. My first thought was that since the diodes are opposite, D2 would be in reverse bias and would act as an open. However, I realized...
  6. K

    Buck converter will power LED's but voltage divider will not....

    Summary: Am seeking help understanding why when I take my battery (50V max 44 nominal; 15aH capacity; 12s5p) and attempt to step down the voltage that sometimes it works and sometimes not... Hi all, New to forum. Chemical engineer seeks help from electrical engineers... Thanks for reading...
  7. R

    Residual voltage on a ground wire

    Dear All, Hope you are fine! Hope this is the right place for this question. If not, my apologies. We just replaced the complete wiring of our apartment with three wires (live, neutral and ground + new circuit breakers + residual current device). Last week I noticed some tickling on my fingers...
  8. E

    Solve Vo: Voltage Nodal Analysis w/ KCL Equation

    I'm asked to solve for Vo for this equation. I've set the bottom node to be my reference node before applying nodal analysis. When included in the KCL equation for node at Vb, will the dependent voltage source 20iΔ be negative since the current through that element is leaving node C? Say, the...
  9. C

    Voltage received by each bulb in a circuit

    Summary: Voltage received by each bulb in a circuit How much Voltage does each bulb receive in the diagram below? (In terms of 1v being the voltage supplied by each cell)
  10. M

    Question about the polarity of a voltage (PHY 2 for engineers)

    My problem is understanding how the polarity of a voltage makes sense. For example, In my textbook, its states that "batteries move negative charges from its negative terminal to its positive terminal. In terms of potential, the positive terminal is at a HIGHER voltage than the negative...
  11. L

    An alternative and odd view of Voltage Drop

    I was going over some fundamentals with my son and I was trying to explain 'voltage drop' - To which appears to be some confusion on the net with respect to terminology. Many people are confusing 'voltage applied' and 'voltage dropped'. First I will explain what I taught - Let us look at the...
  12. Bheshaj

    Voltage drop: What do we mean when we say that voltage drops across a resistor?

    What do we mean when we say that voltage drops across a resistor?and what does it mean when we say that a point is at lower potential as compared to some other point?Can we say that potential is potential energy per unit charge?
  13. Zahid Iftikhar

    Voltage across R, L and C vs AC Voltage source in RLC Series Circuit

    One property of series resonance circuit is that at resonance, the voltage across circuit elements R,L and C may be larger than the source voltage. I can relate it to vector analogy where component vectors may have larger values than the resultant and the phenomenon is counter-intuitive. This...
  14. Zahid Iftikhar

    Why does a capacitor charge to 63% of the applied voltage?

    Statement of problem is given in the summary. Mathematics proves time constant is calculated from the equation V= V0 exp t/RC I want to know if there is any physical explanation of this effect. Please guide me on this. Regards
  15. 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
  16. S

    Set up the differential equation showing the voltage V(t) for this RC circuit

    Hi all. I have another exam question that I am not so sure about. I've solved similar problems in textbooks but I have a feeling once again that the correct way to solve this problem is much simpler and eluding me. Especially because my answer to a) is already the solution to c) and d) (I did...
  17. E

    I want to use high voltage (about 3kV)

    Hi, I want to make a electron gun, and I have to use high voltage(about 3kV or more). But I think I can't use general electric wire. So I want to know what kind of electric wire should i use to use the high voltage??
  18. epotratz

    I Voltage between electron and proton in ground state hydrogen atom?

    I’m not sure if this belongs in classic or quantum physics... but here it is...Is it possible to calculate the “voltage” between an electron and a proton in a ground state hydrogen atom?I know the ionization energy is 13.6 eV, so I assume it's safe to say the voltage is 13.6 volts at a certain...
  19. Guidestone

    Request for historical background on the concept of voltage

    Hi all. I'll get to the point. I've been interested in electricity since I was in college. Concepts such as current and resistance seemed easy to grasp for me but voltage remains a little bit obscure. It's thanks to this forum (specially forum members Jim Hardy r.i.p and SophieCentaur, sorry if...
  20. B

    Chrysler 200 2011 Voltage Problems

    My car burnt out my battery and alternator so I replaced the alternator and now the stereo system is dead when the car is turned on and the alternator is running at 18volts
  21. sergiokapone

    Potentials (and ##\Delta\phi##) of nearby converging bodies

    Let ##Q## - charge of one of conductor, ##\phi_1## --- potential of charged conductor, ##\phi_2## --- potential of uncharged conductor. For the charged conductor: \begin{equation} \phi_1 = D_{11}Q , \end{equation} for uncharged conductor: \begin{equation} \phi_2 = D_{21}Q \end{equation}
  22. H

    How much ripple voltage for an LED is noticable?

    Hi! Question about LED power supplies. They all have marked ripple voltage. Typically 150mV. How much ripple voltage is human eye capable of noticing when looking at LED strips? And is there difference between 12V and 24V? I have opinion that 150mV ripple on 24V LED strip would give the same...
  23. K

    Electric Circuts (Voltage, Ohms, Amps)

    I made a chart and this is my attempt. I am not sure that I am doing the calculations right thou
  24. kolleamm

    How can I change voltage instead of current?

    I have a micro controller that reads voltages from 0V to 5V I did some tests on a potentiometer and I couldn't seem to get any readings of values in between. (range is 0-255 ,, 0 is for 0 volts and 255 is for 5V) Therefore I'm assuming the voltage is staying the same as it turns but the current...
  25. Efeguleroglu

    Why RMS for the average voltage in AC current?

    We write rms formula as $$v_{rms}=\sqrt\frac{\int_a^b[f(x)]^2dx}{|b-a|}$$ I know if we take arithmetic mean average voltage will be 0. So we want all voltage values to be positive. Why don't we do that: $$V_{average}=\frac{\int_a^b\sqrt{[f(x)]^2}dx}{|b-a|}$$ That's first what I did...
  26. J

    Voltage divider rule for CMOS in 0-state and leakage current

    I use the voltage divider rule as output voltage = Voltage across R1 = 5 * ( 0.5 / (0.5 + 20) ) This comes as 0.122 V I'm not sure why they've mentioned I leakage and does 0-state have any impact on answer.
  27. F

    Engineering Draw the magnitude and phase angle of a voltage in this AC circuit

    My solution is attached below. I am not sure if my answer is correct or not , I want to confirm it.
  28. X

    Computing AC voltage in a complex filter

    Problem Statement: Computing AC voltage Relevant Equations: cut off frequency, ac voltage. Hey guys, Amazing to be in this group ! Please find attached the diagram of the problem. E = 10kV at 60Hz, C1 = 60pF and R1 = 1k. I have to compute the ac voltage in reference to ground at point [1]...
  29. D

    Question: Voltage Multiplier Safety

    I want to build a safe Villard cascade voltage multiplier so that I can create sparks that I can touch without dying or being injured. Is it possible to do this? And if so how would you construct it (specifically what capacitors and rectifiers and power source would be used)? My second question...
  30. J

    Voltage Swing for NMOS: Digital ICs by Jan M. Rabaey

    Ref: Digital Integrated Circuits by Jan M. Rabaey I have trouble understanding two things: 1) Why will x charge to Vdd - Vtn1 and why not Vdd? 2) If x in left charges to Vdd - Vtn1, then in right also it would charge to Vdd - Vtn1... so Vy would charge to Vdd - Vtn1 - Vtn2... so why have they...
  31. P

    How to calculate the voltage induced in a coil by an AC magnetic field?

    So, as it says in the title, I am trying to calculate overall voltage induced in a coreless coil in the cases of it being stationary and moving in an alternating magnetic field. To go more into detail, I would like to create a mathematical model of a coil in an alternating magnetic field that...
  32. P

    Get the Voltage from the I(A)-Time diagram

    The area under the diagramm is the capacity.Q=I(A)*t(s) How can I can get the Voltage so tha I get the energy of the battery and capacitor?
  33. Peter Alexander

    Engineering Compute the voltage gain of this bipolar junction transistor circuit

    This is the given schematic. The result should be $$A_u = \frac{R_b g_{21}}{1 + R_b g_{22}} = -50$$ and the way I wanted to tackle this problem is by stating $$A_u = \frac{-R_b i_2}{u_1} = \frac{-R_b (g_{21} u_1 + g_{22} u_2)}{u_1} = \frac{-R_b (g_{21} u_1 + g_{22} u_2)}{g_{11} u_1 + g_{12} u_2}...
  34. J

    Engineering Voltage across the output resistor for this opamp circuit

    Here is question: Find voltage across R3 options: 10V 11V 5V 2V Attempt: No current flows through Opamp, so 1mA flows through R3, this gives voltage across R3 = 1ma * 1K = 1V. But that is not in option. Where am I wrong? No current flows inside or outside opamp, right?
  35. 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...
  36. Rob45327

    What are the voltage and current in motor brushes?

    Summary: I'm rewiring an antique 1 amp universal motor (AC or DC). The two field coils need new brush leads so I have to buy new wire for them and I don't know the voltage. If the motor is running on 110 Volts is it 110 volts at the brushes? The motor is speed is variable and mechanical...
  37. runningman19

    Design of an Op Amp Circuit for Voltage Amplification

    Hi Everyone, I would like to measure voltage output from a sensor via an Arduino. The sensor outputs 20 mV at max capacity. I'd like to bump this up to around 5 volts so it is easier to measure. My plan was to use a non-inverting topology coupled with an LM393N op-amp. The schematic for a...
  38. M

    What is the Relationship Between Veb and Ie in a PNP Transistor?

    The problem: My attempt:
  39. S

    AC Current versus AC Voltage on the Neutral Wire of AC Mains

    Sir how can one explain with the help of an analogy to a grade 10th student the reason behind not getting a shock on touching the neutral wire of the household AC circuit, even though the current flows alternately through live as well as neutral wires.
  40. 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...
  41. Tesladude

    What is the voltage across this capacitor, inductor and resistor?

    I can solve for the questions in completely series or parallel circuits however having the capacitor and inductor in parallel while the resistor stays in series is stumping me completely.
  42. EEristavi

    Why a DC power supply doesn't have a voltage with respect to ground?

    I see that DC power supply have voltage between it's + & - and its 24V. However, there is no voltage with ground. I don't understand - if device's "point" has some potential, why doesn't it give some voltage with ground (which has ~0 potential) I tried this with phoenix contact...
  43. T

    Why can an electron go through PVC insulator

    I connected a PVC insulated alligator clip test lead to a 12V (give 20V) DC power supply positive terminal and a multimeter. After that I connected an other one to the multimeter ground, and a third one to the power supply negative terminal. I turned the multimeter to DC V measure mode. When I...
  44. N

    Electrical Where Can I Find a High Voltage DC 30kv - 40kv Generator for My Experiment?

    Hi all Trying to carry out an experiment and need a high voltage supply Looking for say upto 40kv dc adjustable generator been looking on the net and only able to find low cost voltage boosters on eBay Or if anyone know of a good website to try Any help would be much apreciated Thanks...Niki
  45. Electgineer

    Can LaTeX help improve the readability of scanned documents?

    I would upload it soon
  46. R

    What Are the Best Data Loggers for Monitoring 3-Phase Low Voltage Parameters?

    Could someone please suggest types of data loggers that can be used to log 3 Phase parameters on the Low Voltage side of a transformer. Thanks
  47. C

    Semiconductor physics: Voltage below forward voltage

    Assume we have a diode closed circuit.We connect the p type region of the diode to the positive terminal of the battery(cathode).We connect the n type region of the diode to the negative terminal of the battery(anode).The voltage of the battery is 0.3V .The diode%s intristic se miconductor is...
  48. E

    Line voltage in 3 phase as single sine wave

    Howdy all. The typical image of a three phase electrical system involves 3 sine waves, phase shifted 120 degrees. These sine waves each, individually, represent the 'phase voltage,' which is to a common neutral in a wye configuration. In this wye configuration the line to line voltage is...
  49. A

    Automatic Voltage regulator rating

    Hello Everyone, I'm here in a country which has a 220v single phase. My wife's $700 Microwave/Convection oven just arrived from the US. The rating of this appliance is: 110v, 1750 watts, 15 amperes. I've talked to suppliers here and was told to buy an AVR with a rating(wattage) 5 times more of...
  50. JKhim

    Kirchoff's Voltage Law transposing problem

Back
Top