What is Electric circuit: Definition and 199 Discussions

An electrical network is an interconnection of electrical components (e.g., batteries, resistors, inductors, capacitors, switches, transistors) or a model of such an interconnection, consisting of electrical elements (e.g., voltage sources, current sources, resistances, inductances, capacitances). An electrical circuit is a network consisting of a closed loop, giving a return path for the current. Linear electrical networks, a special type consisting only of sources (voltage or current), linear lumped elements (resistors, capacitors, inductors), and linear distributed elements (transmission lines), have the property that signals are linearly superimposable. They are thus more easily analyzed, using powerful frequency domain methods such as Laplace transforms, to determine DC response, AC response, and transient response.
A resistive circuit is a circuit containing only resistors and ideal current and voltage sources. Analysis of resistive circuits is less complicated than analysis of circuits containing capacitors and inductors. If the sources are constant (DC) sources, the result is a DC circuit. The effective resistance and current distribution properties of arbitrary resistor networks can be modeled in terms of their graph measures and geometrical properties.A network that contains active electronic components is known as an electronic circuit. Such networks are generally nonlinear and require more complex design and analysis tools.

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  1. Z

    Circuit with potential difference across battery being zero?

    Using KVL we have ##\epsilon_1-\epsilon_2+iR=0##. It seems that ##\epsilon_1,\epsilon_2##, and ##R## are given and the only variable is ##i##. Thus, ##i=\frac{\epsilon_2-\epsilon_1}{R}## for the KVL equation to be true. However, it seems like when we think about what happens to this circuit...
  2. Z

    Why does amplifier sink power for Vout>0 and sources power for Vout<0?

    TL;DR Summary: How do we show that the dependent current source in a single-stage amplifier sinks power for ##v_{\text{out}}>0## and sources power for ##v_{\text{out}}<0## I am trying to solve a problem set from MIT OpenCourseWare's 6.002 "Circuits and Electronics" course. There is a problem...
  3. Z

    Linearizing a circuit with a nonlinear element

    I think I managed to solve the entire problem, as I show below. My main doubt is about item (e), the incremental circuit. Part (a) Using the node method and KCL we reach $$\frac{v_I-v_A}{2}=10(1-e^{-v_A/5})\tag{1}$$ Part (b) We can simplify (1) to $$v_A=5\ln{\left ( \frac{20}{v_A+20-v_I}...
  4. Z

    What does a Zener diode do in a circuit with non-ideal voltage source?

    Part (a) The circuit in figure 1b is linear. It is a simple voltage divider circuit. The relationship between a voltage source ##V_I## and output voltage ##V_O## is $$V_O=\frac{R_LR_{IN}}{R_L+R_{IN}}V_I$$ This relationship is true individually and independently for the DC voltage source and...
  5. Z

    Does a signal called "EN" stand for something special in this circuit?

    If it is simply a signal like A, B, and C then the function represented by this circuit is ##\bar{(AB+C)EN}##.
  6. Z

    What are the voltages generated from this current source?

    Here is the circuit and the v-i characteristics KCL gives us ##i_S=i_1+i_2##. Thus, (a) and (b) are solved quickly by noting that for ##v\in [0,1]## we have ##i_1+i_2=0## so ##v## can't be in this interval for a positive current. If we try ##v\in [1,\infty)## then we get...
  7. Z

    Plot ##i_A## vs ##v_A## characteristics for this nonlinear network

    I am quite stumped here. This is what I did so far. 1) The first thing I did was to forget about the terminals to the left and the diode, and to write the circuit as a Thevenin equivalent circuit. Then I put in the diode. However, the terminals we are interested in are lost when we do this...
  8. milkism

    Complex RLC Circuit Problem (System of diff eqs)

    The following circuit is: Going clockwise the current ##I_1## goes through resistor ##R_1## and voltage ##V_11##. Current ##I_2## goes through capacitator ##C_1## and ##R_2##. Current ##I_3## goes through resistors ##R_3## and ##R_4##. Current ##I_4## goes through resistor ##R_5##, but from...
  9. Z

    Two networks described by v-i graph: Find voltages when interconnected

    This problem is from problem set 2 of MIT OCW's 6.002 "Circuits and Electronics". There are no solutions to these problems sets, so I am posting here in case anyone spots mistakes in my solution. Here are the two interconnected networks and their ##v-i## graphs Here is the roadmap for this post...
  10. F

    Engineering Ordinary Diferential Equations in electric circuit

    It's a multiple choice exercise and I have managed to find the characteristic equation V0(t) which is ##V_0(t)= C_1e^{-t}+C_2e^{-3t}## Initially I thought that it was a non homogeneous ODE, but doing the math for the right part of the equation, I found out that it equals to 0. So, I need help...
  11. Z

    I An attempt to understand the associated variable conventions in circuits

    Consider the following circuit The first thing we do is to label each terminal of each circuit element. We use the labels + and -. We could assign these differently (and I will do this in a second example further below), but for now let's stick with these labels. Next, we assign terminal...
  12. G

    B How is surface charge accumulated?

    let's discuss copper wire all along so we only focus on the specific wire. Let's discuss 2 cases(case 1 is hopefully correct, so if it is, would be good to mention it). I'm sorry that this text got so bigger(didn't expect it), but wanted to mention my thought process. Somehow, none of the...
  13. V

    Potential difference between 2 points in a capacitor circuit

    In the given circuit, a transient current will flow and when this current finally stops at equilibrium, the charges ##q_1## and ##q_2## are assumed to deposit at the capacitor plates as shown below. The dashed line indicates an isolated system that will have it's total charge conserved. If I...
  14. P

    I Measuring Low Resistance: Why Meter Bridge is the Preferred Choice

    Why meter bridge is chosen over post office box to measure low resistance?
  15. sol47739

    Am vs Fm variable capacitor receiver, what is the difference?

    What is the difference between a variable capacitor in a AM receiver and a variable capacitor in a FM receiver? I understand that Am is amplitude modulation and that the signal is carried over a changing amplitude and that the frequency is constant. And the opposite in FM signals. And a variable...
  16. EmmyBamidele

    Can someone recommend a relay for me?

    I have a 30V - 100A power supply that I want to control using a -/+ 10V NI DAQ. I want a relay between the current output of DAQ and the power supply. Please advise the specification of relay to use. I'd appreciate a comment on how to connect it also.
  17. G

    Potential difference of an electric circuit

    The figure is: I have the solution to this problem: We have two distinct branches $$V_a-V_b=\overbrace{(V_a-V_c)}^{\textrm{INI}-\textrm{FIN}}+\overbrace{(V_c-V_b)}^{\textrm{FIN}-\textrm{INI}}$$ They have different intensities: ##3\, \textrm{mA}## and ##2\, \textrm{mA}## ##V_A-V_C\rightarrow##...
  18. T

    I Energy of an electron in an electric circuit

    When an electron flows through a circuit say 250V, does it mean the electron possesses 250eV at any time or does it give out a total of 250eV
  19. samy4408

    I Why in an electric circuit with only a generator the resistance R=infinity?

    Why in an electric circuit with only a generator the resistance R=infinity? [Newbie's post edited by a Mentor to delete extraneous embellishment]
  20. Xiao Xiao

    Engineering Nodal Analysis of a circuit with 3 sources and 3 resistors

  21. Xiao Xiao

    Engineering Finding V and I in a simple circuit

    So I know I have to use kirchhoff's Voltage Law so when I apply it's: -12+4i+2Vo-4-Vo=0 and Vo=6i so --> -16+4i+2(6i)-(6i)=0 but apparently that's wrong and Vo should be =-6i and so when I substitute it in the equation it should be -16+4i+2(-6i)-(-6i)=0 and I don't understand why.
  22. Xiao Xiao

    Engineering Electric Circuit Analysis of this First Order R-L Circuit

  23. Ale_Rodo

    "Barlow's wheel" used as an electrical generator

    In this thread, I hope to find some help in understanding one of the first application of Faraday's law of induction: the "Barlow's wheel". Basically the machine converts electrical power to mechanical, so as you can imagine, a battery, some conductor wires, a horseshoe magnet and a metal wheel...
  24. Xiao Xiao

    Engineering Finding Vc for two circuits, Electric Circuit Analysis question

  25. Xiao Xiao

    Electric Circuit Analysis, Nodal Analysis and finding Voltage.

    Summary:: The image shows two circuits, in the first one, using Nodal Analysis we find that V1=4.8V, but in the second circuit V1=10 because using KCL - 10+V1=0. I understand what happened in the first circuit, but I don't understand what happened in the second one, they look the same to me...
  26. Xiao Xiao

    Engineering Help in Electric Circuit Analysis -- One current source and a resistor network

    o9
  27. Xiao Xiao

    Help finding Thevenim Equivalent - Circuit Analysis

    Summary:: So I found Vth=1.19 using Nodal analysis and I'm not sure if that's right, I'm trying to find Rth now but I'm confused as to what to do, any tip that tells me at least from where to start is appreciated. Edit: so I did 12||60 so Rth=10 ohm, is that correct? Is Vth correct too?
  28. A

    Finding a good descriptive model of the electric circuit (for 8th graders)

    Since this quesstion popped up in this thread I thought it might be better to create a new thread: https://www.physicsforums.com/threads/a-question-about-an-electrons-movement-in-a-dc-circuit.997736/ The question is the following: What kind of descriptive model could/should one use while first...
  29. PhysicsTest

    Power Calculation of general electric circuit

    I am trying to calculate the power calculation of a general circuit with voltage leading the current by a phase difference of ##\theta##. The instantaneous voltage is given by ##v = V_m\sin(\omega t +\theta) ; i = I_m\sin(\omega t) ##. The instantaneous power is then ##p = V_m I_m \sin(\omega t...
  30. A

    Electric Circuit: Path of Least Resistance

    I figured that when you close the switch the current from the upper cell will travel through the closed switch due to it being the path of least resistance, essentially the resistor between cells is unused (was my first thought). I'm not entirely sure how to progress with this question.
  31. Vossi

    Electric Circuit Differential equation help

    I'm confused at the part how 4Vc and 48 cos(60t) are deduced, that's all.
  32. E

    Could you check this Li-ion charging circuit?

    Can secondary cell can be described in circuit simulator?? With other symbols like capacitor. Also I wonder if there's a program that provide secondary cell(like Li-ion battery). Please help me
  33. A

    Calculation with this electric circuit (battery and resistors)

    Hey, I am struggling a bit, als I try to solve this problem - I‘d say all five statements are correct, but it is said, that one must be incorrect
  34. Adesh

    How can electrons flow all the way through the circuit?

    Electric currents and the things within are generally explained through the help of intuitive water current examples, where potential difference is explained through the pressure difference and electric current is explained as the flow of water. But I like to think in terms of some driving force...
  35. MARIAM507

    Electric circuit -- Ohm's second law

    I want to know ohm's second law i search many times about it but every time the result is about ohm's first only, so can anyone help me??
  36. K

    Calculate the current in all parts of this electric circuit

    In the circuit below, the output is 23 W across the resistor with the resistance 6 Ohm. Calculate the amount of current in all parts of the circuit as well as the polarity and EMF ε of the unknown battery. Circuit: My attempt: I get 6 unknowns with 5 equations. I don't know how to find the...
  37. A

    How to Solve an Electric Circuit Like This?

    Can someone please tell me to find R of this electric circuit? Please tell me the step-by-step. I have many problems of electric circuit like this. If you show me one, perhaps I can solve the rest of them.
  38. J

    When a short-circuit exists, how to find the current?

    I am not an English speaker, I apologize that I cannot use English well. I have a question calculating the IN. When the terminal a-b is short-circuited, is it right that the currents are zero at 2 ohm and 6 ohm resistances?(Because they are parallel with a short-circuit.) Also, because the...
  39. L

    How to find the equivalent resistance of this electric circuit?

    Summary: How to find equivalent resistance of the electric circuit? I need to solve the following problem: Calculate equivalent resistance of the circuit (figure1), if all six resistances are the same: r1 = r2 = r3 = r4 = r5 = r6 = 100 Ohm. True answer: 66.6 Ohm. I tried to solve this...
  40. baywa2

    Determine the capacitor value so that this circuit is in resonance

    L=100mh=0.1H ω=10^3 rad/s -> f = 159Hz XL= ωL= 2πfL= 2π*159*0.1= 99.90 Ω Z parallel = [(XL∠90º)*R2] / [(XL∠90º)-R2]= 37.13∠-21.8º XC= 1/ωC= 1/(2 π f C) I don't see how I am supposed to get to C
  41. M

    Electric field in a circuit with a DC source

    So I understand that when an electric field is produced in a conductor of length L, the net electric field in the conductor will be 0 because the rearrangement of electrons in the conductor results in the production of its own electric field which cancels out the one produced initially...
  42. E

    Draw an electric circuit potential graph

    Hi. I have physics homework that I don't understand. Hopefully, someone here can give me some advice. So, the homework goes like this: Draw an electric circuit potential graph and find out the potential difference between points B and C. The two resistors have equal values. Believe me or...
  43. Shivang kohlii

    Engineering An electric bulb of 500 W at 100v is used in a circuit

    If the circuit has 200 V supply. The resistance R that must be put in series with bulb so that it draws 500 w is? 2. Relevent equations P= v^2/r I = v/r 3. My attempt at the solution R= V^2/P r (bulb)= 10000/500 = 20 ohm Now for 200 v supply .. P= 500 W V= 200V Rnet = 20 + R R+20= 80 R= 60...
  44. O

    How to fix this electric circuit

    Homework Statement I'm not sure if the construction of this circuit is correct, so that both lamps, which are the same, shine equally brightly. Otherwise only the resistors are given. If it's wrong, what else would it look like? And why?[/B] Homework Equations I guess the laws of Kirchoff...
  45. F

    Basic question about current in an electric circuit

    Let's say we have a basic electric circuit consisting of a battery with some potential difference, and a loop of wire. The wire loop also has some segment with a higher resistance. Now since there is a potential difference, the free electrons will move to make the circuit equipotential. The...
  46. Santilopez10

    Circuit problem involving sources and resistors

    Homework Statement The currents ##I_{{a}}## and ##I_{{b}}## of the circuit have values 4A and -2A in that respective order. A) Find ##I_{{g}}## B) Find the power dissipated by each resistance C) Find ##V_{{g}}## (voltage drop across the current source) D) Show that the power delivered by the...
  47. Santilopez10

    Untangling a Confusing Circuit: Solving Kirchoff's DC Laws

    Homework Statement It’s a rather confusing circuit, I’m having problems trying to understand the way current circulates through the circuit. Homework Equations Kirchoff’s DC circuits laws only, no resistive simplification neither nodal analysis The Attempt at a Solution I’ll attach my intent...
  48. S

    Electrical Component with the Letter M?

    1. Homework Statement This is the sample answer to the circuit they ask to draw. I get the comparators, the inverter and the Gate. That’s all clear. Then they wanted a switch that needs to be used to end the sound alarm, regardless of comparator output. I assume this the box labelled M...
  49. J

    Which way do I measure the potential difference

    Homework Statement All the bulbs in the circuits are identical, as are all the batteries. Rank the magnitude of the potential difference between points M and N. Homework Equations V=IR The Attempt at a Solution My most fundamental question is actually which way do I know to take the...
  50. H

    What's the current from this circuit? Is it a short circuit or not?

    Homework Statement Pic A, what's the I2? Pic B, what's the current across a-b ? Homework Equations V = I*R Voltage in series is different, the current is the same Current in parallel is different, the voltage is the same The Attempt at a Solution from Pic A, I found that I1 = 1A, I3 = 1A...
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