Circuit Definition and 1000 Threads

A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by excess current from an overload or short circuit. Its basic function is to interrupt current flow after a fault is detected. Unlike a fuse, which operates once and then must be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation.
Circuit breakers are made in varying sizes, from small devices that protect low-current circuits or individual household appliance, up to large switchgear designed to protect high voltage circuits feeding an entire city. The generic function of a circuit breaker, or fuse, as an automatic means of removing power from a faulty system is often abbreviated as OCPD (Over Current Protection Device).

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  1. F

    Troubleshooting Neutral Cables in Electrical Circuits

    Last weekend I was in my friend house to change an outlet from 127V to 220V. This means changing the neutral terminal from the bar inside the electrical board (dont know if that's the right rem in english) into a phase. However, I couldn't identify which neutral cable was from the circuit I...
  2. SalahAhmed03

    Sٍٍhort circuit simulation using ANSYS Maxwell

    How to make a short circuit in stator winding of electrical machine using ANSYS Maxwell? Any information will be highly appreciated.
  3. S

    Engineering Please help me with this circuit question using the superposition theorem

    I have tried many times to solve this network, but can't understand how to get current in each resistors by superposition theorem. Please help me to solve and find currents in each 3 resistors with solution. Note:- The figure is attached below.
  4. C

    Why a 20 Ohm lightbulb won't light up in a closed circuit?

    When using the voltmeter and ammeter to investigate the circuit, it was found that the batter had a current of 0.67 A, the two 30 Ω bulbs had a current of 0.17 A, and the two 10 Ω bulbs had a current of 0.50 A. In terms of voltage, each bulb had a voltage of 5 V. When the switch was closed, the...
  5. boysenbeary

    Engineering Finding Time Constant T Without L for an LR Circuit

    Edit: Picture of the Circuit (Simple RL circuit) The value of L is not given. Attempt to Solve for T by Rearranging Equation 1: I rearranged the equation to solve for T, using Ohm's Law so solve for I = V/R at each time. https://www.desmos.com/calculator/qlb2n6w4bg This graph is...
  6. D

    AC - Node Voltage Method for difficult circuit

    Hi! I'm trying to understand and solve this circuit by Node Voltage Method. I have to calculate u(t). In my mind, I don't have any idea if any current should go through Z1 in my calculations. I would be grateful if you could write even equations for this circuit. Is 'a' just a prefix to multiply...
  7. bardia sepehrnia

    Engineering Calculating Power Factor in an AC circuit, given voltage and current

    My attempt at solving this question: I realized my attempt is wrong however I just don't know how to proceed in the first step. How can I calculate the phase shift? and find Voltage and Current in phasor form??If I know that, then I can use power factor formula: pf=Pav/V*I
  8. bardia sepehrnia

    AC Circuit Analysis: Solving Example with Confusing Concepts

    I'm reading this chapter in Electrical Engineering book regarding AC circuit analysis where there is a solved example which I've attached, but there are some concepts that are confusing me. First, why and how do we know that the phasor value of voltage is: -pi/2 Note: I do understand that...
  9. X

    Engineering Find di/dt and dr/dt for a DC circuit with indepedent current source

    Dear PF, I am trying to solve practice problem 8.2. I am stuggling with part B of the question which asks us to find diL(0+)/dt, dvC(0+)/dt and dvR(0+)/dt. My attempt can be seen below. Before t=0 the 4A current source is not present and thus it is an open circuit. A capacitor acts as an open...
  10. X

    Engineering Find di(0+)/dt and dv(0+)/dt of circuit containing resistor, inductor

    Dear PF, I am trying to solve practice problem 8.1 and I am stuck on part b which asks us to find di(0+)/dt and dv(0+)/dt. Down below in the picture is my attempt. Before t=0 it is quite intuitive since the inductor acts as short circuit to steady-state DC and a capacitor acts as open circuit...
  11. X

    Engineering Step response of RC circuit with independent voltage and current sources

    Dear PF, In the figure down below is Q7.47 which asks to determine the voltage v(t) across the capacitor for t > 0. Since it is given that V(0) = 0 there are two scenario's which is between time interval 0 < t < 1 and t > 1 according to the independent sources. For the scenario 0 < t < 1 the...
  12. icesalmon

    Engineering Determine Io and Vo in the circuit

    I am calling the voltage at the node the 2ohm resistor VA at Node A: ( VA - 54 ) / 3 + ( VA - Vo ) / 1 + (VA - 0) / 2 = 0 at Node Vo: (Vo - VA) / 1 - 2*io = (Vo - 54) / 2 io = VA/2 at Node A: Vo - VA)/1 - 2*(VA/2) = (Vo - 54)/2 Vo = 4*VA - 54 Node A: (VA - 54)/3 + VA - (4*VA - 54) + VA/2 = 0 VA...
  13. J

    Harmonic Motion Problem - Finding oscillation of charges in a circuit

    So since V(cap) + V(ind)=0 then Q/C + L dI/dt=0 Now since I=dQ/dt, I can replace dI/dt with d^2Q/dt^2 resulting in Q/C + L d^2Q/dt^2 =0 Now L d^2Q/dt^2 looks like a harmonic motion thing I can solve, where w^2=L. This means I can find w. I get 0.0005385. Now my issue is using this w gives the...
  14. A

    Finding the resonant frequency of this "discriminator" demod circuit.

    This is the FM demodulation "discriminator" circuit. It is one of the simplest analog demod setups one could think of. An RF (FM) voltage signal is applied at V12 and the voltage at ' a' ' is supposed to contain the AF signal in its amplitude. The idea behind the circuit is that it resonates at...
  15. Mondayman

    Intro Physics Textbook on Electronics and Circuit Analysis

    Hi folks, I'm looking for a solid introductory book on electronics and circuit analysis. I have seen The Art of Electronics highly recommended. I will likely get it but as a supplement. Does anyone know of any other good electronics textbooks? I don't mind old textbooks. Some of the newer...
  16. B

    Engineering Drawing the Schematic for a Circuit I built on a Breadboard

    Here is the circuit i have built on a breadboard (link) - Breadboard circuit i am now trying to draw the circuit for this but struggling Hi, I have built this circuit on a breadboard and have tried to draw it out but I am pretty sure its not right, needs to include- 741 amplifier,transisitor...
  17. Kaguro

    RC circuit using complex numbers

    The impedance Z = R -j/wC + ##\frac{1}{\frac{1}{R} - \frac{\omega C}{j}}## But,1/wC=R So, solving this, I find: Z= 3R/2(1-j) |Z| =##\frac{3R}{\sqrt 2}## I =##\frac{V_i \sqrt 2} {3R}## Vi - IR-IXc =Vo Solving this, ##Vo = V_i -\frac {V_i \sqrt 2}{3} - \frac{V_i \sqrt 2}{3R} \frac{-j}{wC}##...
  18. B

    Circuit Requirements Questions (Design of a stadium lighting system)

    [Thread moved from a technical forum, so no Homework Template is shown] A controller is required to monitor the natural illumination of a sports stadium and, when the ambient light is below a pre-set level, to switch on external lighting. The system is required to be of high integrity, and...
  19. 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...
  20. T

    A question about an electron’s movement in a DC circuit

    I have been thinking of the nature of the electric current , or the motion of electrons in a copper cable of a closed DC circuit. Recently I learned the speed of electron is very slow in the copper cable and in a AC circuit the FREE ELECTRONS are in fact moving back and forth. But in a DC...
  21. F

    Simulate a Chopper of Class A circuit in MATLAB Simulink

    I tried to simulate the circuit but I got unreliable results. Here's what I got when I set the duty cycle to be 20%: Stop Time = 0.02 The efficiency is more than100%. Here's the parameters: Could someone please let me where is my mistake?
  22. cianfa72

    Circuit theory - Resistor function for dynamic non linear circuits

    Hi, I'm reading the following paper (L. Chua) about the state-of-art of dynamic non linear circuit analysis -- Chua_Dynamic_Circuits I've a doubt about Theorem 2 on section 3.2 On the Existence of the Resistor Function that establishes sufficient conditions for the existence of network...
  23. J

    Understanding Complex Circuit Configurations

    Having more difficulty understanding the concept, thus I am not showing values. What is causing me confusion is the line in the middle. The first aR and bR are obviously in parallel, but the second aR and bR confuse me. I tried calculating the equivalent resistance from the first aR and bR and...
  24. asd852

    How to determine the number of meshes and loops in a circuit?

  25. asd852

    Circuit analysis involving parallel and series conditions

    par
  26. asd852

    How do we determine whether circuit element is negative or positive?

  27. lekh2003

    Electrical How to use capacitors in a Solenoid circuit

    I've been working on designing an experiment over the past few weeks as part of a school project, under the supervision of a teacher. I have designed a small low-power coil-gun. I have a coil of roughly 60m 24 AWG copper wire wrapped around a length of 2.5cm of clear PVC pipe. I tested the...
  28. 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...
  29. A

    Engineering Circuit Analysis -- How many independent equations can be written using KCL?

    I think there are 4 essential node. So we can write 3 KCL independent equations.
  30. madafo3435

    Understanding Short Circuit Current Paths in Electrical Circuits

    My reasoning is as follows: with the short circuit present, a 0 resistance can be considered between the terminals. Then, since the only objective of the short circuit current ##I_{SC}## is to give information about the Thevenin equivalent resistance and the open circuit voltage (the existence...
  31. propvgvnda

    Find the supply voltage of a ladder circuit

    Find the supply voltage of a ladder circuit shown, so that I=7A. Assume R=11Ω. (The unit must be placed) Hello, everyone. Please, help me with this. Could someone explain to me how to solve such tasks. I literally spent the whole day watching Khan Academy and trying to figure out how to solve...
  32. S

    Engineering How to solve a circuit mystery box?

    How can I solve a ciruit mystery box only knowing there are 5 identical resistors inside. I have two boxes to solve, one they're all in serie and the other is a combination serie and parallele. Each mystery box has 6 nodes and i can connect 2 nodes at a time to an ohmmeter. If i take the one...
  33. S

    How to solve a circuit mystery box

    How can I solve a ciruit mystery box only knowing there are 5 identical resistors inside. I have two to solve, one they're all in serie and the other is a combination serie and parallele. My mystery box has 6 «plugs» and i can connect 2 plugs at a time to an ohmmeter. I've been trying for days...
  34. R

    I LRC Series Circuit with an AC Source

    Attached is the section from the book. I am doing section 31.3 We know that an AC source gives a sinusoidal varying current, and as far as I know its always given by ##i(t) = Icos(wt)##. Its like we take the current to be the base of all other quantities, so we use it to derive everything else...
  35. PhysicsTest

    Static power bridge motor drive circuit

    I am referring to the application note from TI, the below is the power bridge circuit. The truth table is as below a. I try the first values of A=0, B=0, C=0 the circuit would then become like this according to me It is open above point O, then how the voltage of ##\frac{-V_{DC}} 2## will be...
  36. 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.
  37. archaic

    Help! Finding Direction of Current in Magnetic Circuit

    I have nearly finished my homework, but am blocking at one of the simplest questions... I'm going to let ##\rho=0.094\,\Omega/m## Since the magnetic flux is increasing, then, by Lenz's law, the current in both loops is counter-clockwise. If we only look at the left loop, then...
  38. S

    Using Kirchhoff's Laws to Solve this Circuit with Voltage and Current Sources

    I have defined 5 currents but I can't seem to solve it. I1+1=I2 (left) I5+1=I4 (right) I2+I4=I3 upper node By KVL I have determined that I2 and I4 are equal, but I cannot determine the specific current across each resistor. Thank you for your valuable help.
  39. D

    Engineering Kirchoff's voltage law applied to this circuit with three loops

    I'm stuck straight out of the gate any help is really appreciated
  40. greg_rack

    Discharge of a capacitor and current in an RC circuit

    I'm having a few troubles understanding a few things about this circuit... Firstly, what does "In light of this, the potential between the resistors is ##16V##" exactly mean? If current isn't flowing, how could there be a potential between resistors? Secondly, how does current flow with the...
  41. greg_rack

    Time constant of a discharge RC circuit, capacity and charge

    So, the only thing which came to my mind in order to solve this problem was actually to write down the equations using the discharge function, being given two instants and their corresponding charges... but doing so I'm unable to find anything. Ideally, I'd say I should find the time constant...
  42. greg_rack

    Final electric potential difference in a circuit with two capacitors

    So, each capacitor must have a different potential difference, given by its capacity and charge... this would cause charge and current accordingly to flow in the circuit. But how do I determine the final potential difference, which would of course be the same for both of them? I have tried...
  43. Vossi

    Electric Circuit Differential equation help

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

    Force on conductors during a short circuit fault

    If I have two parallel bars serving as a DC bus with a capacitor across the output and there is a short fault event, I know the peak current is limited by V/X. The instantaneous current would be a function of the time RLC time constant. How do I relate this to the force on the conductors due to...
  45. Andrei0408

    Equation Demonstration -- Comparing a pendulum's motion to an LC circuit

    I've just learned about simple harmonic motion and I've been given the following examples: The physical pendulum (for small oscillations sin(theta)~theta), with the formula (1st pic), and the LC circuit, with the formula (2nd pic). If possible, I need the demonstration for these 2 formulas...
  46. T

    Problem with this Laser diode circuit

    I have dismantled an old DVDRW drive and taken a 4-pin laser diode from it. After connecting it to two 2A batteries (red with positive, and blue with negative), the light beam is diverging, and the brightness is even dimmer than another laser diode that I got from a presentation pen. Also...
  47. Ozen

    Increasing the Battery Life of an LED Circuit

    Hello Everybody! I am new to electrical engineering and only had 1 formal intro class on the subject (albeit I did very well in it) and have found myself in a position where I need to design a circuit for a micro reflex sight I have been designing. So let me first describe how my competitors...
  48. K

    Comp Sci Need help finding the resistor size for a circuit (Ohm's law)

    I know there is a serial and parallel circuit I know R1 = 2k, R3 = 1k and i know Vout which is 1V. And i know 5V is coming from supply. I need to calculate the size of resistor R2. I can calculate : 1) IR1 = 5-1V/2000ohms = 2mA 2) UR1 = 0,002A*2000ohms=4V voltage drop on R1 How do i go on...
  49. E

    What is the voltage in a parallel circuit?

    Potentials in points E, F, A, B are equal because there is no resistance. In my opinion, losses of potential energy in the resitors R1 and R2 are not equal (potential C ≠ potential G). Then why do we say that voltage in this circuit is the same?
  50. T

    Need help with a Kirchhoff's Laws circuit problem

    I wasn't taught how to do it at A-Level in-detail, because there are no questions that expect you to use them in a circuit problem. They only need you to know what the first and second laws are in words (i.e. conservation of charge and energy). I tried looking it up on YT, but it's confusing...
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