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. C

    Engineering Laplace Transform on RC circuit

    Homework Statement Homework EquationsThe Attempt at a Solution I'm kind of lost now, how do I go about getting this into the right form for partial fraction exapnsion. And also what do I do with the V(0'). There was no information given about it.
  2. G

    Getting negative current on Zener Voltage Reg Circuit

    i've built a bridge rectifier with a Zener Voltage regulator. 12V peak secondary 3300uF Capacitor 1k ohm load 1k ohm series resistor for the zener and a 1n4728A Zener diode. i'm getting a 2.8V steady voltage, but when i measured the current going through the load with my DMM it's measuring...
  3. P

    Unsolved Circuit Question: Ammeter Reading and Potential Difference

    Homework Statement So here is a circuit question that I couldn't solve Homework Equations V=IR The Attempt at a Solution So I assumed that since the ammeter gives no reading it should lead to no potential difference in between those two points, then I'm completely stuck. Please help, the...
  4. T

    Retired Railroader Explains Easiest AC Circuit Theory

    I am retired from a major railroad co. where I worked on electronic weighing equipment. I have an associate of applied science degree from a local university. I have a basic understanding of dc and ac electricity but the explanation I recently read on this forum was the easiest to understand...
  5. Drakkith

    Engineering Energy Dissipated in an RL Circuit

    Homework Statement In the circuit shown in (Figure 1) , the switch makes contact with position b just before breaking contact with position a. As already mentioned, this is known as a make-before-break switch and is designed so that the switch does not interrupt the current in an inductive...
  6. J

    Inserting a conductor in a parallel-plate capacitor

    Consider a parallel plate capacitor formed by two plates of length ##L## and width ##d##, separated by a distance ##e##. There is a vacuum in between the plates. Let's note the capacitance of this arrangement ##C_0##. I insert a conducting plate of length ##l=L/2##, with ##D##, and thickness...
  7. Sainvictus

    Examine the following circuit. Now complete the table.

    Homework Statement Homework EquationsThe Attempt at a Solution
  8. G

    How do you find the current going through a weird circuit?

    Homework Statement Homework Equations at point C: i2 - i3 - i4 i2 = i3 + i4[/B] The Attempt at a Solution I labeled all the currents going through each resistor in the picture[/B] for loop ABC: 2000i1 = 3000i2 + 4000i3 for loop BDC: 3000i5 = 2000i4 + 4000i3 at point C: i2 - i3 - i4 i2...
  9. M

    Question about circuits with transistors (current, voltage)

    Homework Statement 1. In Figure A-1 of Experiment 18, assume that Vdc = 8Volts, R1 = 1kOhms, R3 = 7kOhms and there is no R2 resistor. Determine the current in R1 when the transistor is fully on and carrying current. Express your answer in mA. 2. In the circuit of Figure A-1, Experiment 18...
  10. B

    How to Derive Impedance in an LCR Circuit at Various Frequencies?

    Homework Statement a. express the equation of motion b derive impedance at the resonant frequency (ω=ωo) c derive impedance at very high frequencies (ω>>ωo and ω>>R/L) Homework Equations Vo=ψ+(R/L)ψ+(1/LC)ψ Z=(1/iω)K(ω) K=1/((s-mω2)+ibω) The Attempt at a Solution Part a was simple, that was...
  11. mkematt96

    Engineering Help finding error in my Circuit Analysis

    Homework Statement Homework EquationsThe Attempt at a Solution My values for i1,i2,and i3 were: -.005179,-.002857 and .004857. When I ran the same circuit through LT Spice the values they gave me were .00059081,.000809628, and .00119037. Where did I make my error? * as a side not I...
  12. anorlunda

    Insights The What and Why of Circuit Analysis Assumptions - Comments

    Greg Bernhardt submitted a new PF Insights post The What and Why of Circuit Analysis Assumptions Continue reading the Original PF Insights Post.
  13. Jayalk97

    Engineering Underdamped Parallel RLC Circuit

    Hey guys, so I'm having trouble with this circuit analysis question. I need to find voltage across the capacitor as a function of time. I nearly finished analyzing but I'm having trouble solving for the initial value constants in the voltage equation. So first I used KCL to create the equation...
  14. J

    Engineering Transformer -- find equivalent circuit from efficiency and V.R

    Homework Statement For 200 KVA, 4000/1000 V transformer. 1 phase. Efficiency is 0.97 at full load and 60% load at unity power factor. No load pf = 0.25 Full load Voltage regulation at 0.8 pf lag is 5% Find transformer ckt parameters for referred to lv side Homework Equations efficiency is...
  15. S

    What Is the EMF of a Cell with Given Energy Dissipation and Current?

    Homework Statement A cell is connected in series with a resistor and supplies a current of 4.0 A for a time of 500 s. During this time, 1.5 kJ of energy is dissipated in the cell and 2.5 kJ of energy is dissipated in the resistor. What is the emf of the cell? A. 0.50 V B. 0.75 V C. 1.5 V...
  16. N

    Engineering Use Circuit reduction, voltage and current divider to find i

    < Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown > in the solution sheet, He took the 18 ohms parallel with the 9 ohms and not the 6 ohms. I don't understand why he took this approach. I was going to take 18 ohms parallel with the 6 ohms and find...
  17. N

    B Solving a Circuit: Neglecting the 1 Ohm Resistor

    I want to know why in this problem in the solution, he disregarded the 1 ohm resistor and found the equivalent resistance of 6 and 3 ohms right away. https://imgur.com/a/efG11
  18. ISamson

    Open-Source uC Circuit Boards -- Comparisons & Conversation

    Hello, Having bought now my Arduino UNO I can't help but notice how many other open-source and similar boards there are (RaspberryPi, CIRCUIT Computer...). My friend has a RaspberryPi 2 and sometimes talks to me about it. I can't help but wonder what is the difference between all these such...
  19. J

    Exponential forcing function to an RL circuit -- poles & zeros

    For reference: Engineering Circuit Analysis, Hayt & Kemmerly, 4th ed, 1986, page 345. Given a series RL circuit, the phasor current is I(s) = Vm/(R+sigma L), where S = sigma, w (omega) = 0. Thus we are dealing with only a exponential forcing function. Obviously I(s) goes to zero as sigma...
  20. M

    Brightness of bulbs depending on their watt level

    Homework Statement Two 110-V light bulbs, one "25W" and the other "100W" are connected in series to a 110 V source. Then: a. the current in the 100W bulb is greater than in the 25W bulb b. the 25W bulb will be brighter c. the current in the 100W bulb is greater than that in the 25W bulb d. the...
  21. D

    How do you calculate the power requirement for a circuit? (laser diodes)

    I have 52 laser diodes, rated 5VDC, 5mW, wired in parallel and powered by a battery, rated 5V, 2A (I measure 2.7). I'm thinking some diodes burn out because as the voltage drops, the current becomes too great. The diodes manufacturer states the maximum operating current of each diode is 20mA. I...
  22. 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...
  23. E

    Determining the equivalent resistence of a circuit

    Homework Statement I want to determine the equivalent resistance between A and D in the drawing below: [/B] Homework Equations 1/Req=1/R1+1/R2+1/R3+... And Req=R1+R2+R3+... The Attempt at a Solution I don't really know how to simplify this drawing, I'm not sure if one resistor isn't...
  24. P

    Engineering Single-Phase Double Circuit Transmission Line

    Homework Statement There are 4 wires with diameter d arranged in a way such that they form a square shape, with the wires on the corners. The horizontal distance is kD while the vertical distance is D. Prove that the inductance per meter of each conductor is 1/2 + 2ln { [2kd√(1 + k^2)] / d }...
  25. Cocoleia

    Conservation of Power in the armature circuit of a DC motor

    Homework Statement I am asked in a lab report to explain the conservation of power in the armature circuit of the DC motor. Homework Equations This is the data I have acquired: The Attempt at a Solution I have been reading around, and I have learned somewhat about the Armature Copper Loss...
  26. P

    Induced Electric Field In Circuit With Varying Resistance

    Homework Statement This is irodov's problem #310 in electrodynamics A long solenoid of cross-sectional radius a has a thin insulated wire ring tightly put on its winding; one half of the ring has the resistance ## \beta ## times that of the other half. The magnetic induction produced by the...
  27. F

    Need Spin Wave Generator Circuit Design

    Hello, I have found the technology of spintronics very interesting with a great potential for the (hopefully near) future & I am desiring to experiment with spin waves. I am sure there are several ways to create a spin wave or current, one of which involves placing a platinum strip at the end...
  28. H

    Capacitor circuit time constant problem

    Homework Statement How long does it take in time constants ( = RC) for the charge on the capacitor in the circuit shown below to reach one quarter its initial value? Homework Equations C=Q/V time constant=RC Vc = Vo * (e)^(-t/RC) The Attempt at a Solution From C=Q/V I get Q=VC so for the...
  29. T

    How does a resistor exactly reduce current flow in a circuit

    Greeting . It is clear to me that the resistor represents a physical obstruction to the passing current I do not know how exactly it works and I will try to show what I was really interested in the diagram.
  30. T

    Engineering How can I simplify this mixed resistors circuit

    Hi I am to calculate Rab of the circuit and I have no idea on how to approach this problem. It would have been all nice and eaasy if it weren't for the vertival 30 ohm resistor. Because of this I'm in a dark spot. I will appreciate any help.
  31. K

    Circuit to detect a modified sinewave

    I wander if yo guys can point me in the right direction here. I need to design a circuit that will differentiate a modified sine wave from a pure sine wave. What I am trying to do here, is design a circuit that will sense when mains is lost and a UPS takes over by monitoring the waveform of the...
  32. T

    Electronic circuit breaker design

    I'm building an electronic circuit breaker as follows, I have some questions about the short circuit protection. I tested it in simulation and it trips in about 11 ms. How would I work out the interrupt rating ?, which I read is the maximum short circuit current the breaker can interrupt...
  33. N

    Conduction Angle of a Diode Circuit

    Homework Statement I am trying to prove that the diode conducts between the expressions shown here: Homework Equations I know that Vo = Vpsin(wt) and the only information i know about the diode is it has a turn on voltage of Von. The Attempt at a Solution I have tried to plug the variables...
  34. H

    Motorcycle starter safety circuit

    I don't know if it's the same for a car but bikes uses a starter relay to set off a starter motor which cranks the engine. Bikes have a side stand for you to lean the bike against when stationary. In case the rider tries to start the bike with side stand deployed (could cause crash if forget to...
  35. Eclair_de_XII

    Finding the resistance in a parallel-series circuit.

    Homework Statement "Find ##R_2## and ##R_3##, assuming negligible resistance ##r=0\frac{V}{A}##." ##R_1=6.1\frac{V}{A}## ##I_1=1.3A## ##I_3=4.8A## ##\epsilon = 24 V## Homework Equations Voltage in parallel circuits: ##V_1=V_2## or ##I_1R_1=I_2R_2## Total voltage: ##\epsilon =...
  36. toforfiltum

    Engineering Simplifying switching circuit literals

    Homework Statement The problem is given in the picture attached. It is a network of switches.Homework EquationsThe Attempt at a Solution I managed to simplify the expression to this: ## (S + x'(w+y) + xvz)(x'+y)(v+z') ## but I just can't find a way to simplify it to 9 literals. I've tried all...
  37. I

    Calculating capacitance from an AC circuit

    This question is from my physics book and neither I nor my teacher can find the mistake in my method. (The original question is not in English so I'll do my best translating it) > When a coffee maker is connected to the wall (230 V, 50 Hz) its power consumption is 180 W. The power consumption...
  38. S

    Ideal conditions in which circuit analysis is done

    What are the ideal conditions in which circuit analysis or analysis of an electrical system is done?I know that the air friction,friction between materials is ignored in ideal systems, such as for ohms law applications.What else is ignored in analysis of ideal electrical systems?
  39. terryds

    Norton equivalen circuit problem

    Homework Statement Determine the norton equivalent Circuit Homework Equations Norton theorem The Attempt at a Solution First, I transform 5A and 10 ohm (in parallel) into 50 V and 10 ohm in series So, there are three meshes, for Mesh 1 (I assume the current is clockwise) ##30 i_1 - 10...
  40. P

    Understanding Resistance and Circuits for Homework Assignments

    Homework Statement My problem is that I don't know how to deal with this kind of questions. Homework Equations V=I*R[/B]The Attempt at a Solution I thought that the overall resistance would increase since there is a hindrance after the lamp doesn't function anymore, but don't know what to...
  41. Drakkith

    Engineering Simplifying a Circuit Using a Y-to-Δ Transformation

    Homework Statement [/B] A.) Simplify the circuit (Figure 1) by using a Y-to-Δ transformation involving the resistors R2, R3, and R5 as shown in (Figure 2) . Determine the resistances of the equivalent Δ. B.) Determine the equivalent resistance Rab in the circuit. Hopefully these two figures...
  42. terryds

    I RL vs LR Circuits: Low-Pass/High-Pass Filters Explained

    Is there any difference between RL vs LR circuit? Which one is for low-pass/high-pass filter? Please help
  43. M

    Engineering Analyzing currents in parallel in circuit diagrams

    Homework Statement Homework Equations V=IR parallel resistance. The Attempt at a Solution All elements are in parallel (teacher confirmed this in explanation to the class). Beginning placing labels for nodes to the right of R1, A, B, C, D, and E (ending before R4) and redrawing it as the...
  44. J

    Engineering AC Circuit Power/impedance question

    Homework Statement For the circuit given in FIGURE 1 the power factor is 0.72 lagging and the power dissipated is 375 W. Determine the: (i) apparent power(ii) reactive power (iii) the magnitude of the current flowing in the circuit(iv) the value of the impedance Z and state whether...
  45. T

    Engineering Solving Circuit Diagram Homework - Test Prep Tips

    Homework Statement [/B] A screenshot with everything given Homework Equations No idea The Attempt at a Solution No idea I'm not sure how to solve this or where to look for a solution. I was given this yesterday and have a test tomorrow. The professor has not gone over this at anytime...
  46. G

    Battery charger circuit fault(s)

    My cheapish 12V battery charger suffered an overcurrent, and now is not working properly. Below is a schematic of the main power side: The MOSFET M1 will not turn on, which I'll tackle later, but even with the drain bridged to source the voltages are wrong. The black, slow charge (rail at...
  47. B

    Heat transfer for an encapsulated circuit

    Hello, So I am assembling some testing equipment. I have an active circuit, microcontroller, and two battery packs inside a black polypropylene case (which is around 1 ft x 1 ft x 0.5 ft). I was performing a thermal analysis because I want to make sure the electronics do not heat up past around...
  48. J

    Engineering AC Circuit Voltage Waveform Analysis

    Homework Statement An A.C. voltage, V, comprises a fundamental voltage of 100V rms at a frequency of 120 Hz, a 3rd harmonic which is 20% of the fundamental, a 5th harmonic which is 10% of the fundamental and at a phase angle of 1.2 radians lagging. (i) Write down an expression for the...
  49. L

    Magnitude of the induced magnetic field in a circuit

    Homework Statement The circuit in Fig. 32-31 consists of switch S, a 12.0 V ideal battery, a 20.0 M resistor, and an air-filled capacitor. The capacitor has parallel circular plates of radius 5.00 cm, separated by 3.00mm. At time t=0, switch S is closed to begin charging the capacitor. The...
  50. D

    Engineering PMOS Circuit Problem: Finding Rs and Input Resistance

    Homework Statement Homework Equations Id=K*(Vsg-Vth)2 KVL The Attempt at a Solution On part A, Haven't had much experience with PMOS. Used large signal model, to find Rs. Equivalent circuit: We know that Vs=0. That means Vd=-7.5 V. If we say the voltage across Rs is Vdd-Vd, then that...
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