What is Kirchoff's law: Definition and 67 Discussions

Kirchhoff's circuit laws are two equalities that deal with the current and potential difference (commonly known as voltage) in the lumped element model of electrical circuits. They were first described in 1845 by German physicist Gustav Kirchhoff. This generalized the work of Georg Ohm and preceded the work of James Clerk Maxwell. Widely used in electrical engineering, they are also called Kirchhoff's rules or simply Kirchhoff's laws. These laws can be applied in time and frequency domains and form the basis for network analysis.
Both of Kirchhoff's laws can be understood as corollaries of Maxwell's equations in the low-frequency limit. They are accurate for DC circuits, and for AC circuits at frequencies where the wavelengths of electromagnetic radiation are very large compared to the circuits.

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  1. P

    Solving a Complex Kirchoff's Law Problem - Mike's Request for Help

    Homework Statement Hello there, hope you are well. I am having trouble solving this problem involving Kirchoff's laws. I have attached a copy of the circuit and problem to this post in jpeg format. Thanks again in advance for any help. Mike Homework Equations The...
  2. U

    KIRCHOFF's Law: Solving Circuit

    according to circuit In Left Loop Current is I1 and Right Loop is I2 Now Loop Left 10-8I1-3I1-I2=0 which becomes 10-8I1-3I1+3I2=0 11I1-3I2-10=0 ------------eq 1 Now Loop Right 15-6I2-3I2-I1=0 15-6I2-3I2+3I1=0 3I1-9I2+15=0 I1-3I2+5=0 ---------------eq 2 Deduct eq 2 from eq 1...
  3. M

    Understanding Current Direction and Voltage Drop in Kirchoff's Laws

    Hi, I've attached an image of the question I'm confused about. I don't know how to determine which way the current flows in each loop. So far I've determined that I1 flows up and I2 goes down. So the loop on the right will be counter clockwise. Because I2 goes down I3 should go up...
  4. JJBladester

    Kirchoff's Law and Critical Points

    1. Homework Statement [/b] What is/are the critical points of Kirchoff's Law: L\left(\frac{di}{dt}\right) + Ri = E The Attempt at a Solution I solved the differential equation above and got the following solution (which I verified to be correct): i = \left(\frac{E}{R}\right) +...
  5. S

    What is the direction of I2 in this circuit?

    What is the current through the 10 ohm resistor? See figure below. The equations I got were: 12=10*I2+5*I1 9=10*I2+5*I3 But I am confused as to how to get the last equation from the junction. Would it be I1 +I2=I3? Once you have the three equations you would combine them and solve for...
  6. I

    Capacitors in series and Kirchoff's law

    I seems very simple, and I'm sure I understood it before, but for some reason I suddenly started to get confused with it when we want to know the capacitance of 2 capacitors in series, we assume they both have the same charge on them, so I just want an explanation to why does it have to be...
  7. A

    Applying Kirchoff's Law in an R-L circuit with parallel resistors

    http://img296.imageshack.us/img296/6961/circuithk7.jpg Assume that the switch has been closed a long time. 1.) Find the current through the inductor before the switch is opened. 2.) Find the voltage in the right resistor before the switch is opened. 3.) Find the current in the right...
  8. S

    Proof of Relationship in Parallel Circuit Using Kirchoff's Law

    Homework Statement How do I prove the relationship between the equivalent resistance of a parallel circuit and the values of the constituent resistors exist? Homework Equations V=IR The Attempt at a Solution Is it because: I total= I1+I2+I3 and V is the same in parallel...
  9. A

    Kirchoff's Law: Which Direction Does the Current Flow?

    Homework Statement determine which way the current goes Homework Equations kirchoff's current law The Attempt at a Solution i say that it is moving away because if i say its positive going into element1 then since its negative its going out of element1 so its moving away from A
  10. N

    Can Kirchoff's Law Solve a Core 2 Duo Equivalent Problem?

    URGENT! Simple Kirchoff's Law Problem - PLEASE HELP! The problem is here. :confused:
  11. N

    Is the following proof of Kirchoff's law correct?

    The standard book used in our university proves the Kirchoff's law of radiation in an elaborate manner...I understand the proof.But I think using the same principles,this can be proved in a much better way: Consider an enclosure is at temperature T and the enclosure is filled with temperature...
  12. F

    Solving Kirchoff's Law for Loop 2: A Homework Challenge!

    Homework Statement http://img353.imageshack.us/img353/4445/kirchoffkq4.jpg Homework Equations The Attempt at a Solution for the first loop (2v battery) the effective resistance is 33/7 the voltage is 2v so current=v/i =14/33 A Now loop 2 is the problem. i don't know...
  13. M

    How can I solve the current in a circuit quickly using Kirchhoff's Law?

    help about kirchhoffs law! :cry: is there a shortcut way to solve the current in a circuit using kirchhoffs law?? or... is there a law or other easiest solution that can solve the the current in a circuit?? because my prof. gave us the equation and solution, but it is too long to solve? hope u...
  14. T

    What guarantee Kirchoff's law of potential difference?

    Kirchoff's law states that, the potential difference along a closed circuit must be ZERO. Now, let's do a simple question 1. We have a simple circuit consists of INDUCTOR and Voltage source-->V=V.sin(wt) At any instant, why must the voltage supplied equal the voltage generated in the...
  15. S

    Kirchoff's law of radiation (very confused )

    kirchoff's law of radiation (very confused!) we have a large evacuated enclosure which is black on the inside maintained at a constant temperature T0. there are two black spheres suspended within the enclosure close but not touching and sphere A is maintained at temperature T1 (T1>T0). when B...
  16. B

    Kirchoff's Law: Exploring the Difference

    I'm having a problem with Kirchoff's law because It seems it can be interpreted 2 ways. Perhaps they both arrive at the same answer, but if you could help me out as to which way to do it or if it matters. 1. the Integral[E*dl]=0, in a closed loop 2. the algebraic sum of the voltages in a...
  17. M

    Kirchoff's Law - Emittance & P-Cygni Profiles

    Hello, I'm new here, but I have a question regarding Kirchoff's law (I think its Kirchoff's law, but I'm not sure). I'm looking at it now, and it says that E=M/Msub b. I know that the equation gives the emittance of an object, but I don't know what emmissivity or emittance is! Any help would...
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