What is Voltage source: Definition and 127 Discussions

A voltage source is a two-terminal device which can maintain a fixed voltage. An ideal voltage source can maintain the fixed voltage independent of the load resistance or the output current. However, a real-world voltage source cannot supply unlimited current. A voltage source is the dual of a current source. Real-world sources of electrical energy, such as batteries and generators, can be modeled for analysis purposes as a combination of an ideal voltage source and additional combinations of impedance elements.

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  1. cianfa72

    I Video: 'How electricity actually works'

    Hi, I found this interesting video about How electricity actually works. The point he makes (see for example the video at minute 7:23) is that the energy in a light bulb connected to a battery is actually transferred by the electromagnetic field and not by electrons flowing through it. The...
  2. G

    I Capacitor connected to voltage source, vary plate separation

    Hi. A plate capacitor is connected to a constant voltage source. The stored energy is $$W=\frac{1}{2}\cdot C\cdot U^2=\frac{1}{2}\cdot \varepsilon_0\frac{A}{d}\cdot U^2\propto\frac{1}{d}$$ if the voltage source remains connected when varying ##d##. So the energy decreases with increasing...
  3. S

    Engineering Intro to Power Systems: AC RLC circuit voltage calculations

    ##V_{S} = 120V ## ##f = 60Hz## ##L = 20mH## ##R = 10\Omega ## (a) Assume the capacitance is omitted. What is the resistor voltage? ##X_{L} = j\omega L = j2.4\pi## ##V_{R} = Vs\cdot \frac{R}{R+X_{L}} = 76.5067-j57.6847## ##V_{L} = Vs\cdot \frac{X_{L}}{R+X_{L}} = 43.493+j57.6847## (b) What...
  4. PhysicsTest

    Voltage source and current source

    As per ohms law the current is generated based on voltage and resistance V=IR. So if 5v and 1k resistor the current 5mA flows in resistor. But if I take a current source, can I pump any amount of current to resistor? So, current drawn is not characteristic of resistor?
  5. S

    Engineering Using Kirchhoff's Laws to Solve a Circuit with Two Batteries

    Okay so This is what I've tried; a) A formula I've found in the lecture notes; $$ U_a = U_q - R_i*I $$ To get I used the ## I = \frac{P}{U} ## formula I get I to be 0,46 A.Now put back in formula for and rearange to get Ri should be $$ \frac{Ua-Uq}{I} = Ri $$ and the solution should be 0,43...
  6. E

    Putting internal resistance in series with a voltage source

    Suppose I have a galvanic cell, where I've arbitrarily set the (-) anode to have a potential of zero volts and the (+) cathode to ##\epsilon## V. The electrodes are connected via the load, but also via the solutions and salt bridge in the centre. Edit: The two trailing wires are connected to a...
  7. garthenar

    Engineering Designing an adjustable voltage source using only resistors and a pot

    I need to create a powersupply that takes in a +5 and -5v and has an adjustable output that varies between -2 and +2 v using one potentiometer. I already came up with a design myself but it did not work. I need some help figuring this out. I think my idea for how to get specific positive or...
  8. R

    Engineering Norton/Thevenin Equivalent circuits with a dependent voltage source

    so when I did this problem I did nodal analysis to find the voltage across the 40k resistor, and found it to be 16V. From there I did two source transformations, combined the sources and did some equivalent resistance to get the answer as seen below: However this differed from the answer he...
  9. 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...
  10. Castello

    Determine the value of the voltage source Vx

    Homework Statement Find Vx, as the 5A current source provides 50W to the circuit. Homework Equations ##P = V.I## ##U = R.I## The Attempt at a Solution [/B] At first, as 5A current source provides 50W, by ##p=vi## there should be 10v through it. Then, i applied KVL and found four equations...
  11. YMMMA

    Electricity: 2 charged rods connected to a voltage source

    Homework Statement In addition to the question given in the attached file below, I don’t understand how is the polarity changing periodically. Homework Equations Concept-based question, I guess. The Attempt at a Solution I have no idea how should I approach the question. So, if anyone has an...
  12. E

    Voltage drop in the internal resistance of a voltage source

    In this circuit,first there will be voltage drop in the internal resistance of the voltage source.Mostly,the voltage source is assumed ideal in circuits,however,here a practical voltage source is assumed. So,there will be voltage drop in the internal resistance of the voltage source which will...
  13. J

    AC voltage source driving an inductor and a capacitor

    Homework Statement Homework EquationsThe Attempt at a Solution I don't understand why would the current be zero in any of the branches . May be I am missing something very fundamental . Please help me understand this question .
  14. E

    Engineering Basic circuit problem -- Resistor network and a voltage source

    Homework Statement http://www.chegg.com/homework-help/questions-and-answers/problem-2-variableh-resistor-r-circuit-fig-p224-adjusted-va-equals-60-v-find-value-r-q8083343 Homework EquationsThe Attempt at a Solution Hi, I attached a pdf file with the problem. My question is, for the lower right...
  15. Drakkith

    Capacitor and Dependent Voltage Source

    Homework Statement Select the correct expression for ##i_o(t)## for ##t≥0^+##. Homework Equations ##V(t) = V(∞)+[v(0)-v(∞)]e^{\frac{-(t-t_0}{\tau}}## ##i(t) = C\frac{dV(t)}{dt}## ##\tau = RC## The Attempt at a Solution I'm a bit stuck on this problem. Specifically, I'm not sure how to deal...
  16. thegreengineer

    Need help with voltage regulator circuit that uses 7805

    Well let me explain. I've finished a circuit that consists in a microcontroller unit (in this case a PIC16F877A) that is connected to a LCD module, a keyboard and a RTC module (via I2C protocol). As far as I know all of them require VCC (=+5V) for operating so I needed to create a +5V regulated...
  17. E

    Checking my answer.... finding the power of a current and a voltage source

    Homework Statement The current source and voltage source in the circuit shown in the Figure below are connected in parallel so that they both have the same voltage, vs. The current source and voltage source are also connected in series so that they both have the same current, is. Suppose that...
  18. G

    Short circuit's effect on a voltage source and a resistor

    If I have a resistor and a voltage source in series but then I apply a short circuit in parallel to both of them would the voltage source and resistor not receive 0 V? Thus having 0 current. What would change in the circuit?
  19. marsupial

    Nodal Analysis with Dependent Voltage Source

    Homework Statement Here is a diagram of the circuit and my redrawing with currents drawn: We are to find the power delivered by the dependent voltage source. I found a solution online, but I am not sure why they had the KCL line as: $$ \frac{v_1 - 160} {10} + \frac{v_1} {100} + \frac{v_1...
  20. ESMAT 1995

    Constant current source Inverter

    i was reading about CSI and the first paragaph said "A constant current source is assumed here, which may be realized by using an inductance of suitable value, which must be high, in series with the current limited dc voltage source. " and it says nothing else about it , so clearly it's a basic...
  21. hackhard

    Work done by voltage source

    Is the work done by a constant voltage source positive or negative when current is opposite to emf?
  22. Bassa

    Initial Voltage in an RC circuit with a Current Source and no Voltage Source

    Homework Statement [/B] Derive an expression for vc(t) in the circuit of Figure P4.13 and sketch vc(t) to scale versus. I attached a screen shot of the circuit for this problem. time. Homework Equations V = IR V = V0exp(-t/tau) The Attempt at a Solution [/B] I am trying to find the...
  23. peroAlex

    Current density of specific configuration

    Homework Statement Two hollow metal spheres (left one has radius of 0.7 meters and right one has radius of 0.4 meters) are half-submerged in the sea water with specific conductance of γ = 4 S/m. Distance between their centers is much greater than their radii dimensions and equals 60 meters...
  24. R

    RC Circuit with a voltage source

    Homework Statement A voltage source E_0 cos ωt is connected in series with a resistor R and a capacitor C. Write down the differential equation expressing Kirchhoff’s law. Then guess an exponential form for the current, and take the real part of your solution to find the actual current...
  25. W

    Non-Inverting Opamp with Voltage Source resistance

    Homework Statement Homework EquationsThe Attempt at a Solution (a) [/B]We can assume for ideal op-amps that there is: infinite input impedance low output impedance the potential for infinite amplification (b) Non-inverting op amp (c) This is the part I have trouble with. There is three...
  26. hackhard

    Ac-dc adapters in series (or parallel)

    multiple 220V to 5v, 2A ac to dc adapters connected to the same 2-phase input terminals input voltage is 220v domestic supply. is it safe to i join output in series to obtain 10v /15v/25v etc. ?
  27. E

    How to do Mesh Analysis with current controlled voltage source

    Homework Statement Vs = 100cos(2000t) Homework Equations KVL, KCL The Attempt at a Solution My mesh equations are: -Vs + I1(30-12.5j)-I2(120j)=0 4Ix+I2(120j+20)-I1(120j)=0 Ix = (I1-I2) Are these correct? When I solve I get a different result than when I do nodal analysis.
  28. E

    Mesh analysis with dependent voltage source

    Homework Statement Find the: -Complex power delivered by source -Power factor of total load -Is the power factor leading, lagging, or in unity?[/B] Homework Equations KVL/KCL The Attempt at a Solution I want to solve this via mesh analysis to get currents. Mesh1: -10V + V1 + 0.75V1 = 0 V1 =...
  29. E

    Superposition with AC voltage source and DC current source

    Homework Statement Using the superposition principle, determine the current i(t. 2. Homework Equations Zc = 1/jwC Zl = jwL V = I*R I = V/Z The Attempt at a Solution First, I converted inductor/capacitor to impedance: L = 1.5H -> jwL = j * 10 * 1.5 = 15j C = 10mf = 1/(jwC) =...
  30. C

    Question on Laplace Transform of a constant voltage source

    Hello. I am reviewing the use of the Laplace Transform to do circuit analysis and I am slightly confused about the transform of a constant voltage source. For example, let's say we have a constant voltage source V1(t) applied to a circuit for a long time - let's say it reaches steady state. We...
  31. terryds

    Circuit problem with two voltage source

    Homework Statement R1 = 2 ohms R2 = 4 ohms R3 = 6 ohms E1 = 10 V E2 = 14 V What is the voltage between point A and B ? A. 0.18 V B. 0.98 V C. 1.34 V D. 1.64 V E. 3.28 V Homework Equations KVL The Attempt at a Solution [/B] I tried using KVL I assume that both mesh currents will go in...
  32. P

    Complex Impedance of a voltage source and 2 resistors

    Homework Statement A real voltage source can be expressed as an ideal voltage source that is in series with a resistor that represents the inner resistance of the voltage source. This voltage source is a EMF and it is also in series with another resistor. Suppose both the EMF resistor...
  33. W

    Series voltage source vs parallel voltage source

    Power systems isn't my area of specialty and I've been doing some reading where it was stated that series voltage connections are safer than parallel connection. I don't fully understand why though. website address...
  34. kostoglotov

    Why isn't this largest voltage source given as negative?

    This isn't actually a homework problem, but it is an example in a my textbook that I have a question about... imgur link: http://i.imgur.com/2OglMH4.png Ok, I wanted to clarify some things. I understand that current flowing from a positive terminal to a negative terminal represents a...
  35. T

    Nodal analysis with dependent voltage source

    Homework Statement In attached image. Just curious as to how their nodal analysis is correct. Homework Equations [/B] ##I_{in} = I_{out}## The Attempt at a Solution Solution in image. I am just not sure how they applied nodal analysis here to find that ##I_s = \frac{12}{12} +...
  36. Y

    Why use arbitrary voltage source in Dependent Thevenin's

    Normally, I would just assume that for a circuit with just a dependent source, I can treat it the same as as one with an independent source. Using Picture 1 Assume that I want to find the Thevenin wrt nodes A and B. I want to find Rth, so I zero out all sources, which makes I = 0A. The only...
  37. S

    Nodal analysis with voltage source

    Homework Statement Use nodal analysis to calculate Va, Vb, and the currents IE1 and IE2 without using source conversions I have tried this many, many times, and I must be missing somethingHomework Equations [/B] The equations I came up with: VA-10/ 1.1 + VA/1.2 +VA-VB/1.4 = 0 VB+2/1.5 +...
  38. terryds

    Circuit problem -- Voltage source and 5 resistors....

    Homework Statement http://www.sumopaint.com/images/temp/xzkaelnnkibopbdq.png The electric current that goes through the 5 ohm resistor is A. 0 A B. 0,3 A C. 0,6 A D. 0,9 A E. 1,2 A Homework Equations 1/Rparallel = 1/R1+1/R2+... Rseries = R1+R2+... The Attempt at a Solution I take the 6...
  39. A

    Determine resonant frequency of an AC voltage source

    Homework Statement Given a series RLC circuit, with one R, one L, and one C element, and an AC voltage source with variable frequency, find the resonant frequency experimentally given an ammeter and a voltmeter. Homework Equations The current in the circuit when the circuit is in resonance is...
  40. M

    Engineering Calculating Voltage Source in AC Circuit

    Hello, I'm currently working on a problem involving the calculation of an unknown voltage source of a circuit containing a resistor, inductor and load in series. Unfortunately, the problem sheet does not give an answer at the end, so I am unsure as to whether my approach is correct -- hence...
  41. I

    Maximum power of circuit with dependent voltage source

    Homework Statement Homework Equations V(oc) = I(sc) * R(th) Kirchoff's voltage law The Attempt at a Solution a) is okay. For part b): After redrawing with the R(th) and V(th) found in part a): Equations of loops: s is I(sc) a is I(left loop) left loop: -8 + a(4000) + (a-s)(4000) = 0 right...
  42. S

    How did Coulomb charge his spheres to verify Coulomb's law?

    We are doing an experiment to verify coulomb's law, and we are currently using a stable voltage source. However, we were assigned to do it using static electricity, and we were wondering how to establish inverse r^2 dependence if the amount of the charge on the ball isn't the same every time we...
  43. Sampad Saha

    What will be the total resistance of ideal voltage source?

    If we connect a single resistor in the circuit of ideal voltage source then what'll be its total resistance? ? Isn't it zero? As shown in image .so is it possible that the total resistance of a circuit is 0 Although it has 5ohm resistor!?
  44. Rampart

    Engineering Zener diode circuit-variable voltage source

    Homework Statement This diode zener has breakdown voltage equal to Vz=8.2V for currents: 75mA<=iz<=1A.If RL=9 Ω,how much must Rs be,so that VL=Vz=8.2V,while Vb changes at about _+10% in relation with the nomimal operating current,displayed in the data sheet which is 12V? The Attempt at a...
  45. B

    Node voltage with dependent voltage source

    Homework Statement http://i62.tinypic.com/245fwxu.jpg[/B]Homework Equations & Attempt to solve [/B] http://i62.tinypic.com/142v6mv.jpg Bottom: A Top left: B Top Right: C(1/100 + 1/5 + 1/25)VB - (1/25)VC + 6.25I = 450 mA (20.8)VB - 0.04 VC + 6.25I = .450 A VC = 45 + 6.25I I know I'm doing...
  46. B

    Voltage/Current Division with central Voltage Source

    Homework Statement Find V0 using voltage/current division Homework Equations V=(VsR)/Req I=(IsIeq)/I The Attempt at a Solution I used general circuit rules (parallel and series) to get the total resistance as 14.775 ohms{?}. And I'm stuck with what to do next . . .
  47. N

    Pn junction diode (series combo of voltage source and diode)

    The question is to solve the current through a resistor after a pn junction. (photo attached) As far as I'm aware the voltage source in the pn junction is (in this orientation) of opposite polarity to that of the 0.8V voltage source. From my understanding the answer goes like: V=IR I=V/R...
  48. Rampart

    Troubleshooting Diode Circuit with DC and AC Voltage Sources: Need Help?

    Hello guys.I am really having a problem with a circuit that includes a dc source,an ac source,2 resistances and a diode(not ideal).In the pdf that i uploaded is my way of thinking for this.I will really value any help and guidance. Thnx in advance
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