# What is Kirchoff: Definition and 36 Discussions

Kirchhoff, Kirchoff or Kirchhoffer is a German surname. Notable people with the surname include:

Adolf Kirchhoff (1826–1908), German classical scholar and epigrapher
Alfred Kirchhoff (1838–1907), German geographer and naturalist
Alphonse Kirchhoffer (1873–1913), French Olympic fencer
Charles William Henry Kirchhoff (1853-1916), American editor and metals expert
Detlef Kirchhoff (1967–), German rower
Fritz Kirchhoff (1901–1953), German screenwriter, film producer and director
Gustav Kirchhoff (1824–1887), German physicist — Kirchhoff's laws in electricity, spectroscopy, thermochemistry.
Gottlieb Kirchhoff (1764–1833), German chemist (died in Saint Petersburg)
Jan Kirchhoff (1990–), German footballer, currently playing for KFC Uerdingen 05
Mary Kirchoff (born 1959), American fantasy novelist
Paul Kirchhoff (1900–1972), German anthropologist and ethnologist of pre-Columbian Mesoamerican cultures
Robert Kirchhoff (born 1962), Slovak film director
Ulrich Kirchhoff (1967–), German show jumping champion

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1. ### Solving Kirchoff's Laws: Are My Answers Correct?

Does anyone know how to do part (a). I labelled the current through R1 I1, I4 through R4, I3 through R3, I2 through R2, and I5 through the 3ohm resistor. I used Kirchoff’s Laws to make the equations I1 + I4 = 8, 2I1 + 32I3 - 14I4 = 30, and I1 + I3 - I4 = 0. I solved these equations by subbing...
2. ### Application Of Kirchoff Law (Desert)

Homework Statement:: Sand is rough and black so it is a good absorber and radiator of heat depending on temperature. During the day, sand's radiation of the sun's energy superheats the air and causes temperatures to soar. But, at night most of the heat in the sand quickly radiates into the air...
3. ### 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...
4. ### Ohm's law and Kirchoff — What am I missing?

[Moved to homework, so no template] Summary:: trying to figure out physics for current and having issues. keep getting something that does not make sense. working on this issue, and i think i have to find ttl resistance, to find current using ohms law. looking at the circuit attached there is...
5. ### There is more to Kirchoff than a law....

Found this brief read on my new feed, thought it would be appreciated here.
6. ### I Huygens principle from Kirchoff Integral (sign doubt)

Consider the Kirkoff integral theorem and the Huygens -Fresnel principle/formula (both from Wikipedia): KIT The Kirchoff integral for monochromatic wave is: U({\mathbf {r}})={\frac {1}{4\pi }}\int _{S'}\left[U{\frac {\partial }{\partial {\hat {{\mathbf {n}}}}}}\left({\frac...
7. ### Direction of current in Kirchoff's second law

Hello, I'm going through Kirchoff's second law, and stumbled across this example on this page: In the image above, you can see that the blue arrows (both arrow 1 and arrow 2) indicate the direction that the current goes in. However, I am wondering why the current cannot go as per the red...
8. ### Hard Kirchoff's Laws problem with batteries & resistors....

Homework Statement Homework Equations Kirchhoff;s first and second law, V=IR The Attempt at a Solution Tried the question as follows: V= 24/(2+6+4) = 24/12 = 2V (pd from top cell) then did 2=4 I3 therefore I3 = 0.5A and then 2 = 6I2 I2 = 0.33A and I1 = 0.5+0.33... =0.83A?
9. ### How does conventional current flow through the first light-bulb?

Homework Statement What way does the current flow through the first light-bulb? Homework EquationsThe Attempt at a Solution This isn't really a homework question but related ot my school work. I'm doing Kirchoff's Laws and normally I would have just thought that the current (if we use...
10. ### Kirchoff's method for a weird circuit

Homework Statement In the following circuit, the battery has emf ε = 12.7 V. The resistors are R1 = 2000 Ω . R2 = 3000 Ω, and R3 = 4000 Ω. What is the current through resistor R2 ? Homework Equations Kirchoff's Rules V=IR The Attempt at a Solution i0 (into A) - i2 (current into resistor 2) -...
11. ### How can I use circuit analysis to prove RI = RSRP/(RS - RP)?

Homework Statement I have to prove that RI = RSRP/(RS - RP) by circuit analysis. The Attempt at a Solution [/B] So I tried to create a system of equations to do this: For the first circuit using kirchhoffs rules: V-IA(RS + RI) = 0 [1] For the second circuit: V-IBRS - IPRP = 0...
12. ### What is the Net Resistance in this Complex Resistor Problem?

Hey there! I'm having some real trouble deciphering this complex resistor problem. I have heard of the Kirchhoff voltage and current rules and do know how to use them to solve some problems but I'm not sure how to apply them in this context, or if they are even used to solve this. As seen the...
13. ### Engineering Circuit (equivalent resistance)

Homework Statement Find the equivalent resistance Homework Equations Req(series) = R1 + R2... Req(parallel)=(1/R1+1/R2...)^-1 The Attempt at a Solution I'm having problems understanding how to simplify this circuit. There should be parallel and series "loops" to simplify but I'm having...
14. ### Calculation of equivalent resistance

Homework Statement : [/B]Given the circuit diagram, find the equivalent resistance between points P and Q. Homework Equations : [/B]ΔVloop = 0, ΔIjunction = 0 and V = IRThe Attempt at a Solution : [/B]Eliminating the wires with no resistors and solving for resistance gives me the answer as...
15. ### Kirchoff's Law - Wire in parallel with light bulb

Homework Statement If you measure the resistance of the three lightbulbs (independently) and get the following values. What is the equivalent total resistance of the circuit, and it’s uncertainty. R_1 = (50 \pm 7) \Omega, \ \ R_2 = (720 \pm 30) \Omega, \ \ R_3 = 140 \pm 20) \Omega Now you...
16. ### Finding the Unknown Resistance Value

Homework Statement The current going through the resistor R1 in the figure does not change whether the two switches S1 and S2 are both open or both closed. The resistances are R1 = 70.00 Ω, R2 = 50.00 Ω, and R3 = 62.00 Ω. The voltage is V = 15 V. With this information, what is the value of...
17. ### Kirchhoff's Current Law: Solving for Open Circuit Voltage

Homework Statement http://postimg.org/image/61e06uo7x/ The question is to find the open circuit voltage Homework Equations The Attempt at a Solution Just wondering why the current flowing through the voltage source was left out for node 1 and the current through the 16 ohm...
18. ### Quick Questions on Electric Circuits (Current directions and Kirchoff)

Hi guys, i need some help here... 1. I know that by convention, the positive charge of the voltage source is taken to be the direction of current, but I'm confused by this MIT lecture vid that drew the current as appearing to be flowing from the negative terminal. You can see the drawing in...
19. ### Kirchoff Rule Sign Conventions, Need Clarity.

Hey all, I am just doing Kirchoffs rules right now. So we have a couple sign conventions we were taught. I just need to make sure my reasoning makes sense for the 3 and 4 rule. 1. When we travel through a source of emf from + --> - we get a - voltage. 2. When we travel through a source of...
20. ### Troubleshooting Circuit with Kirchhoff's Laws

Hello, I am quite confused about this circuit: http://tinypic.com/view.php?pic=1zvtnxf&s=6 It's quite possible, that this circuit doesn't make any sense, it was made by me, out of curiosity. I know there is a junction, but from there I just can't set up any loops which would make any...
21. ### Two simple questions about equivalent resistance and kirchoff laws

two simple questions about equivalent resistance and kirchhoff laws! pleaseeeee! :D EQUIVALENT RESISTANCE: Hi everybody . greetings from Peru.I know it's a dumb question but help please .please read below Homework Statement For the network shown in the figure, show that the resistance Rab =...
22. ### Desperately needing help on a simple Kirchoff problem

Hello people, this time I request your help for a fairly easy question, but a crucial one for me. To be honest I wasn't full awake when my teacher in university was talking on this topic( :( ), so I don't know how to solve it. Homework Statement Given on attachment. (Superior paint skills...
23. ### Kirchoff voltage law to transistor circuits?

Homework Statement I want to know how to arrive at the equation for the base emitter side and collector emitter side of a transistor using kirchhoff voltage law. Homework Equations Kirchoff voltage law is \sumV = \sum IR. Please refer my attachment in which i have to arrive an equation...
24. ### Using Kirchoff rule to find Voltage drop and current, in a complex circuit

Homework Statement Measure the Voltage drop and current in all element of the circuit, given the figure which has the following Resistance and its Ideal emfs; R1=20ohms, R2=70ohms, R3=55ohms, R4=45ohms, R5=30ohms, R6=20ohms, R7=70ohms, E1=15v, E2=5v, E3=5v. Homework Equations...
25. ### Kirchoff Laws: Voltage & Current Detailed Help

Pls anyone can Give me full detail of Kirchoff Law of Voltage and Current pls,,,
26. ### Why is my method of using Kirchoff Voltage Law wrong?

Homework Statement The question asks for current I1 and I2. Homework Equations The Attempt at a Solution I managed to get the answer using KCL at a few different nodes, but I am unsure why my first attempt was wrong. For question 3a, I tried using KVL at the left most mesh. My...
27. ### Kirchoff's Law Problem: Finding Currents in a Parallel Circuit

Kirchoff Law Problem (please help me):( I need help trying to find the current I1 which flows through R1 and the current I3 that flows through R3. Given: E1=8V E2=4V R1= 110 R2=40 R3=50 R4=50 I figured out that the first equation is: I1=I2+I3 The 2nd equation...
28. ### Green's Function - Kirchoff Helmholtz Integral Problem

I'm seeking help in understanding Kirchoff-Helmholtz Integral. Actually what i am facing the problem here is, i don't understand certain things about Green's 2nd identity which stated that two scalar function can be interchanged, and forming the force F = \phi\nabla\varphi -...
29. ### Non conservative electric field and kirchoff law

in circuits involving inductors can we use kirchhoff law ? i have seen this in many books but the electric field inside inductors is non conservative !
30. ### How Do You Solve Kirchhoff's Loop Equations for Currents I1, I2, and I3?

My professor gave us the three equations for a circuit and said to find I1, I2, and I3 However, I cannot figure out how to solve it. The equations: I1 + I2 = I3 5 - 10*I1 -10 - 5*I3 = 0 5 - 5*I2 - 5*I3 - 10 = 0 Every time I try to solve it I end up with two unknown variables. How would you...
31. ### Solve Kirchhoff Problem: Find Voltages of Resistors

Homework Statement http://img178.imageshack.us/my.php?image=questionel8.jpg". I am tasked to find the voltage of all the resistors using Kirchhoff Current Law and Voltage Law. TAKE NOTE THAT I AM NOT ALLOWED TO USE MESH ANALYSIS which means I need to assign current for all resistors...
32. ### The AnswerUnderstanding Kirchhoff's Laws and Sign Conventions for RL Circuits

about kirchoff? Homework Statement can anybody explain why we write kirchhoff laws on RL circuit like -Ldı/dt -iR=0 shouldn't it be written like -Ldı/dt +iR=0 Homework Equations -Ldı/dt -iR=0 -Ldı/dt +iR=0 it is about signs and how we know inductans' poles + or -...
33. ### Kirchoff theorem in graph theory

i read a little bit of the syllabus in my university graph theory course and i just wonder if the the kirchhoff theorem in graph theory has any application to kirchhoffs law in direct current in electricity?
34. ### Understanding Kirchoff's Law in A/C: Application and Explanation"

Whether Kirchoff's Law Is Applicable In A/c.then Say How?
35. ### What Is the Correct Spelling of Gustav Robert Kirchhoff's Last Name?

Help, please? What is the correct spelling for the last name of Gustav Robert Kirchoff (Kirchhoff? Kirschoff?) Thank you!
36. ### Why do the imaginary parts of phasors in Kirchoff's Laws add to zero?

Something's bugging me. Suppose we take kvl around a loop in a circuit, we have: v1(t)+v2(t)+...=0 Suppose v1, v2, v3(t) are all sinusoidal (they can be written as Acos(wt+s)). So we have A1cost(wt+s1)+A2cost(wt+s2)+...=0 Suppose we replace all of them by their phasors, this should...