What is Circuit: Definition and 1000 Discussions

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. johnsmith7565

    Engineering First Order RL Circuit: Finding a Current I2(0-)

    I shorted the inductor and performed mesh analysis. The solutions to the linear system were done using a calculator. The book says that the value for i2(0-) should be 15 mA but I'm getting -2mA. What am I doing wrong? I'm completely confused. Maybe mesh isn't the most efficient way to find I2...
  2. Purpleshinyrock

    Engineering Circuit analysis on a supernode

    Hello. Can someone give m e pointers on how to find the value of vx given that it is inside a supernode(will it be the valueof the voltage inside or the difference of potential between the two nodes?): here's the exercise and what I've done so far attached. Your time and attention are deeply...
  3. J

    Find the current through a complicated circuit

    Yeah so I'm confused about this circuit because it has an overlapping path. My guess is that the current doesn't flow in one of the two paths in the middle but I don't have a good reason for it (I don't know why). I suppose there is symmetry but I haven't been able to find good videos on...
  4. altruan23

    Engineering Why is a differential amplifier considered the same as a subtractor?

    So after using superposition and setting the ratio R2/R1 = R4/R3 the same or R2=R4 and R1=R3,i come to the eq. for output voltage Vout= R2/R1 * (V2-V1) or R4/R3(V2-V1). And in the book foundations of analog and digital electronics by agarwal and lang, they are saying that this circuit is a...
  5. altruan23

    Engineering Opamp adder circuit: Where does the "-" come from?

    So i used KCL and both currents are flowing into the node, and then leaving together to go to the resistor R3. So my eq can be seen in the picture. I was looking in a book and they had a minus infront of the parantheses. Is the current flowing from R3 into the node??
  6. altruan23

    Engineering OPamp circuit - how to simplify this term?

    So this is the circuit. And here i tried to calculate Uout/ Uin , any suggestion how to simplify this term?? I used Uout= Uin * (1+ Z2/Z1)
  7. bluesteels

    [Ohm's law] Why does the answer key use the time after 5 seconds?

    This the answer key:: im confused because it say "how much energy has been dissipated after 5s". So shouldn't you be looking at the ground after 5 sec. but apparently the solution look at it before 5 sec, am I missing anything, can someone explain
  8. altruan23

    Engineering Constant current source transistor circuit - differences between 2 types?

    So basically we can have a constant current but i don't understand this circuit. for example: i can have the Ia what ever I want with current divider rule: Ia = Iq * R2/R3. So Ia is proportional to the ratio of R2/R3. And if i give a resistor at the collector terminal, if i change it between...
  9. N

    Engineering Help with my Karnaugh map circuit: it does not work

    Hi! Good night ;) I have made the simplification of my circuit from the truth table using maps of. Everything looks good, however the simulation does not work in many cases according to the truth table. I notice that my boolean equation taken from the maps looks very big, is there the error...
  10. altruan23

    Engineering Op amp circuit -- Did I calculate the output voltage correctly?

    can someone check, if i calculated the output voltage correct? i used virtual ground because V+-input of the op amp is 0 --> V- input is then also 0.
  11. bluesteels

    Power formula for circuit when another resistor is added in

    On Chegg they solve for V using P=V^2/R using 36W and R1= 25Ω, which is equal to 30V then they add R1+R2 = 40Ω and they plug in P=V^2/R and solve for P which is 22.5W I'm confused on why they didn't use P=I^2*R cause you know the system is in series so I is the same and solve for I then...
  12. altruan23

    BJT emitter circuit weird equations?

    Summary:: So apparently the equations schould be correct but I am not sure about it. Isnt R1 = Ub(10V) - Base voltage / Iq + Ib --> Ub is the source voltage 10V. And schouldnt R2 be :base voltage / Iq?
  13. kaiiliana

    Changing capacitance effect on ripple in full rectification circuit

    [Mentor Note -- thread moved to the schoolwork forums] Hi. So I'm a Physics HL student in IB and I'm designing a circuit for my Physics IA. (think of it as a lab/project if you're not familiar with IB) I'm required to have an independent variable of 7 dif. values and a dependant variable. For...
  14. N

    Engineering (A+B)(A+C)=A+BC circuit doest not work (protoboard)

    Hi guys :)! I have a little problem with my homework protoboard circuit: First, i try to connect the simplification (A+BC), the LED it doest not turn off and not response when i push the buttons. All the components its ok, all its works. If the simplification works, the complete expression...
  15. Amaterasu21

    B What Happens When You Connect Different Voltage Batteries in Parallel?

    Hi all, I've been thinking about a hypothetical circuit with (say) a 6V cell of negligible internal resistance, a 4V cell of negligible internal resistance, and a resistor in parallel with each other, and I can't figure out what the potential difference across the resistor would be. I've tried...
  16. Raihan amin

    Understanding a heat sensor circuit?

    What I understand is that the β parameter of the npn transistor is temperature dependent. Increasing the temperature increases the collector current and hence the LED turns ON. But I don't understand the resistor arrangement.Also I can see that the diode is keeping the Base-Emitter junction in...
  17. V

    Determining inductive reactance from a 3-phase AC circuit

    I am trying to figure something out, but I am in the first step and just trying to get through my "thought experiment". Let's say I have a 480V 60hz 3 phase supply feeding a circuit that comprises of nothing but the conductors themselves (effectively a shorted power supply). Consider the...
  18. S

    Finding potential at a point in capacitor

    I tried solving the part (a), and got I =1.82 A for the current value using Kirchoff's law. Next, I want to use Ohm's law to calculate the voltage at point a. Va = IR In this equation, will resistance R correspond to 4.4Ω or 8.8Ω? How do you determine which resistance to use when solving this...
  19. elektro2021

    Engineering Simulating this cascoded NMOS logic circuit

    I need help for following exercise from Rabaey - Digital Integrated Circuits: A Design Perspective Size and simulate the circuit (IMAGE BELOW) so that it achieves a 100 ps delay (50-50) using 0.25 μm devices, while driving a 100 fF load on both differential outputs. (VDD = 2.5V) Assume A, B and...
  20. S

    Using Kirchhoff's Rule - Theory question

    In my lecture, it was explained that Kirchhoff's Rule is used when circuits are too "complicated" to simplify by combining resistances in series and parallel. I do not understand in which cases I can simplify circuits by combining resistances, and on which cases I can only use Kirchoff's Rule...
  21. S

    Why is it important to classify circuits as series or parallel?

    The answer sheet assumes that the resistors in both circuits are in series and that we need to use the equation Req = R1+R2+R3.. to find the Req in both cases. How come the resistors are in series, when there are multiple resistors in a single row? Also, why does the following work yield the...
  22. P

    Find the total power developed in the circuit given the readout

    Here is the problem with my power calculations in blue. My reasoning is that + terminal is higher potential, − terminal is lower potential and if the reference goes in the direction of decreasing potential then p=vi and if it goes against the decreasing potential then p=−vi. I've applied this...
  23. miyelmunshi

    Engineering RC circuit where source depends on capacitor current

    I did a kvl loop and got V + 5Io - 15 Io = 0 So, V = 10Io Then, substituted dq/dt for Io and q/c for V I get to dq/dt - 50000q = 0 solving this equation i get q = C x e^50000q (c for constant) my Io = dq/dt so Io now is 50,000Ce^50000q now my Q(0) is 3 x 10^-5 So my Io (0) should be...
  24. 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]
  25. NoahCygnus

    How to use Kirchhoff's voltage law on this circuit?

    In this circuit, I have to find the potential at point O. I tried using Kirchhoff's voltage law for the three open loops AOC, AOB and BOC to arrive at potential at O. According to my calculations the potential at O should be 0, but that is not the case according to the source. So I must be using...
  26. johnsmith7565

    Engineering Finding the constraint equation of a circuit with a dependent voltage

    What I’m stuck on is finding the constraint equation for i on the top question . I don’t know how to find it when it’s through a voltage source and not over any resistors. (I can’t use ohm‘s law) After I find i the problem should become easy to solve. I know that v1 = 10 and v2 = 20i . The KCL...
  27. Y

    Calculating Values for PN2222A LED Circuit

    I'm going to be adding an IR LED to my Arduino Uno and I'm trying to wrap my head around the math used to figure out the exact resistor values needed to use a PN2222A transistor to drive the LED.I know my LED has a voltage drop of 1.35V and I want to run it at 100mA and that I'll be supplying it...
  28. Eobardrush

    Help in solving an electricity circuit problem involving Kirchoff's law

    My initial solving method was taking 1.75A and adding the resistors at the 1st loop(4 and 8 ohms) to get the answer V=IR V=1.75(4+8) V=21V But the answer sheet uses 0.75A instead of 1.75A to find EMF of E1. So according to the answer sheet its V=0.75(4+8) V=9V 0.75A is the answer for the i)...
  29. P

    How Does Deriving V = dW/dq Explain Voltage in Circuit Theory?

    The statement "The net charge on every component in the system is always zero. Thus no component can collect a net excess of charge, although some components, as you will learn later, can hold equal but opposite separated charges" leads to believe that we are always dealing with charges of...
  30. DenDanne

    Construct a Moore Circuit for Binary String '01' Detection: Step-by-Step Guide"

    Summary:: I have a problem getting the circuit of the problem to a Moore-solution. "Construct a Moore Machine and show it in a circuit, that outputs '1' whenever the sequence '01' is encountered in any input binary string (using D-flipflops)". First of, I have written the Moore Machine. I...
  31. simphysics

    Single Loop Potential difference -- sign issue

    Hello everyone, I've been struggling with this problem for 1 hour so far. homework-and-exerciseselectric-cir
  32. Xiao Xiao

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

  33. johnsmith7565

    Engineering Current Divider Circuit (Find a Resistance)

    The resistors are all in series , with exception of R, so I added them together and then used the current divider equation to solve for R, and I got 720 ohms. The textbook says R should be 30 ohms. I’m completely lost.
  34. qwertypo

    Why in this short circuit geometry can I not sense a photocurrent?

    Hi, I'm wondering why shorted circuit geometry like figure 2 did not sense photocurrent? Even if the the circuit composed like 2, I guess that by the Kirchhoff's Law, voltage should apply to the ampere meter and photocurrent should be sensed. But in real experiment, I found that shorted circuit...
  35. minhha04

    Analyzing a frequency-mixer circuit in LTSpice

    Summary:: I'm trying to analyze a frequency-mixer circuit using LTSpice but i keep bumping into problems. Am I understanding something wrong? so I'm trying to design a frequency-mixer circuit. (the images are all shown below) in LTSpice, and there's a task asking me to perform a transient...
  36. Stonestreecty

    Heavy Amplifier Circuit Oscillation Happened

    Hi, all I am experimenting with audio amplifiers for a while now. I learned how to do an operational amplifier with discrete components and understand all its section and sub-circuits, recently. Then I decided to just skip the hard part and use operational amplifier and output power stage for an...
  37. D

    Engineering Input and Output Impedance of circuit

    Hi, I have a circuit with 3 transistors I want to rewrite to a small signal model. When multiple transistors are in the circuit I get confused how to do it. This is the signal model and small signal model I have. Is it wrong?
  38. Ugnius

    RL circuit after switch has been opened

    Hi guys , I've been trying to think this one out but I'm drawing a blank. What I am able to understand that I'm required to calculate the backwards emf when the switch is opened. The current through the resistor R1 is 9mA. I was wondering if 9.2mA is even possible? Can the current exceed Imax...
  39. G

    Equivalent Capacitance and Resistance of this Circuit

    NOTE: THE C1 that is 120 microfarads is meant to be C3. What I did first was find equivalent capacitance of C2 and C3 by doing (40)*(120)/(40+120)=30. Then I found Ceq by doing (20)*(30)/(20+30)=12. For the resistance I did 6*3/(6+3)=2, for R2 and R1. Then to find Req I did (5)*(2)/5+2= 10/7 Am...
  40. K

    A Understanding Proportional Counter Circuit

    Hi, I am a graduate student currently studying on the topic of simple gas filled proportional counter. In the effort of trying to make my own system, I ran into this problem that how should I connect multiple counters to one single preamp correctly (and cheaply). This is the circuit I'm working...
  41. ergospherical

    Justifying the peak closed loop gain of an op-amp circuit

    I'm just looking at a Bode plot of log(gain) vs log(frequency) for a an amplifier circuit. I'm trying to figure out whether I'm expecting to see a resonance in the gain at the frequency where I measured one. How could I, in principle, work out theoretically where the peak gain should occur - is...
  42. Franklie001

    AC circuit analysis involving resistors and inductors

    Summary:: Hi anyone can explain me how to solve this circuit, finding the current I2 and I1? Really don't know where to start Thanks
  43. REEEEEEEE

    How should I Approach this Circuit Calculation?

    Homework Statement:: R1 = 2kOHms; R2 = 2kOHms; R3 = 3kOHms; R4 = 3kOHms; VS = 25V; IS = 10mA [5,5] a) Determine the power provided by the source dependent on current using method of the nodes [3.0] b) What is the value of electrical power dissipated in all resistors in the circuit? Relevant...
  44. S

    I Do electrons flow in an electrical circuit?

    The video on youtube on the above link seems to imply that electrons don't flow through a circuit. At 01:29 into the video, the narrator says that he used to teach his classes how electrons move through a circuit by using a clear plastic tube with a chain inside of the clear plastic tube. The...
  45. M3D1

    B To confirm if I am correct about the role of voltage in a circuit

    i just finished some basic concepts about electricity and wanted to confirm if my deduction/understanding is correct: in a simple circuit of let's say a battery and lamp,motor,resistor, the difference between potential of two ends of battery(voltage) say how much potential energy per charge has...
  46. A

    Circuit Design Help: Progress & Resources

    My progress so far: https://www.multisim.com/content/NV8Ndn6gdNtxbJFroJ8FFN/atempt2/open/
  47. M

    Engineering Kirchoff's Law Problem about this Induction Generator circuit

    Hi, Please find attached below the Induction Generator circuit. I have the following parameters: Parameter Value Rs = Rr (Resistance on stator and rotor) 0.2 Ω Ls = Lr (inductance on stator and rotor) 5 mH = 0.005 H p (number of pairs of poles) 2 f (frequency) 60 Hz Vsl (stator line...
  48. L

    I Explaining Current Behavior in an LC Circuit

    Without mathematical formulas, but only with a "Physical intuitive meaning", why if at t=0, I have a charged capacitor, and I connect it through a wire ,forming a closed path, to a inductor the current increasing with time and his derivative decreasing? To me seems like the inductor oppose "to...
  49. M

    Engineering Induction motor calculation problems

    Given the following input parameters: Parameter Value Rs (Resistance through stator) 1.4 Ω Rr (Resistance through stator) 0.7 Ω Ls (stator inductance) = Lr (rotor inductance) 0.002 H xs = xr = 2*π*f*Ls 0.6283i Ω Lm(magnetic inductance) 0.01 H xm = 2*π*f*Lm 3.1415iΩ f (frequency)...
  50. PhysicsTest

    Inductor Circuit Simulation: Understanding Current Rise and Voltage Output

    I am trying to understanding the inductor circuit. I have drawn the below circuit and try to simulate The Inductor current comes to 500mA and Vout is 5V as per simulation. The current in inductor should slowly increase from 0A to 500mA but i cannot see that in the waveform. Is my understanding...
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