# What is Kirchhoff: Definition and 64 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. ### A Diffraction theory, power density and angle of incidence

Hello everybody I am currently looking at diffraction through a rectangular aperture. I am looking at an aperture which is large compared to wavelength, and am looking at diffraction at all angles behind the aperture in a distance which is approx equal to the size of the aperture. I am...
2. ### Kirchhoff Voltage Rule Problem

I tried doing three loops. For the bottom I did 9-I1(1) + I2(1) - I3(10) -12 = 0, for the upper left corner I did 12 - I2(1)- I2(5) = 0, for the upper right corner I did 9 - I1(1) - I1(8) = 0. I came to I1 =1, I2 =2 and I3 = .2. This was incorrect, I don't think I am summing the currents...
3. ### 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...
4. ### Numerical Evaluation of the Kirchhoff Integral (Flux Pattern) (Units?)

Naturally there are vector equivalents of the Kirchhoff Integral. Taken from Jackson (10.113) ##\vec{E} \left( \vec{r} \right) = \frac{ie^{ikr}}{r} a^2 E_0 \cos \alpha \left( \vec{k} \times \vec{\epsilon}_2 \right) \frac{J_1 \left( \sin \theta \right)}{\sin \theta}##Where I just let ##\alpha =...
5. ### Finding the current and voltage for a resistor

I tried to solve it by loop currents. So on the left mesh the loop current ##I_1## goes clockwise and on the right mesh the loop current ##I_2## goes counterclockwise. I ended up with the following equations: 1) ##V_1-R_1(I_1+I_2)-R_2I_1=0##; 2) ##V_2-R_3I_2-R_1(I_1+I_2)=0##. To find the...
6. ### Removing connections between equipotential points in solving circuits?

A sketch of the setup and the equivalent circuit are attached. I believe the correct way to solve this is to redraw the circuit as shown in Fig. 3 and then remove the connections between evidently equipotential points, which reduces the problem to a familiar setup of in parallel and in series...
7. ### A Using the 2d wave equation or the Kirchhoff plate equation

I would like to model the dynamics of a plate. Is it ok to use just the 2d wave equation if the plate will be under tension and fixed at the boundaries? I am a bit confused what the point of the Kirchhoff plate equation is in that case, is it for when the plate is self supporting? Many thanks
8. ### A Kirchhoff problem: Find the currents and voltages in this circuit

Homework Statement In the circuit of the figure, determine the intensities I1, I2, I3, I4, I5 and the voltage Ug. Homework Equations Superposition and Kirchoff The Attempt at a Solution 20-10I1+5I3-10I1=0 5I3+Ug+5I5=0 20I2+10I2-150=0 From the last equation, 30I2 = 150, I2 = 5 A KNOTS...
9. ### Engineering Fundamentals of Electric Circuits - Sadiku Question on KVL

Hi, this is my first time posting, I'm glad there is a space like this where we can share our doubts and hopefully get some help from other students. As you can see on the image above, there's a KVL applied to the circuit in practice problem 2.6, but my question is the following: On equation...
10. ### Kirchhoff's First Law to solve a circuit with 2 loops

Homework Statement I've recently watched a video which explains Kirchhoff's first law however, I'm not sure about his calculations. I got the same answer just wanting to make sure I am doing it right. the guy wrote L1: -75I2 +3V=0 ⇒ I2= -3/-75=0.04A He calculated L2 like -12V -125I3 +75I2=0 ⇒...
11. ### 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...
12. ### Writing Kirchhoff Rules for a Multi-Loop Circuit

Homework Statement I need to write Kirchhoff rues for the following circuit. This is not for a physics class, but for a programming class. I can do that part, but I am not sure if the equations are correct. Homework Equations The Attempt at a Solution V1-I1*R1-(I1-I2)R3-I1*R2=0...
13. ### The Kirchhoff diffraction formula with small wavelength

Homework Statement The fresnel-kirchhoff diffraction formula could explain diffraction,I think it should also produce the result with relatively small wavelength and large width slit in which case there is no diffraction. Homework Equations...
14. ### Find the current and Voltage of the following pieces

Homework Statement Above is the circuit I have to deal with. We are given the Vin = 6V, Vout = 3.367 V and all the R values. We are asked to find the remaining values (The I's and V's) Homework Equations [/B] Kirchhoff Voltage and current laws V = IR R's in series add Voltage from a source...
15. ### Calculating Node Voltage using Nodal Analysis

1. Homework Statement The circuit is driven by a voltage source, Vs(t)= 8.2 cos(1.8 t − 0.25 )V . The circuit elements are given as follows. G1= 5 S,G2= 7.6 S,G3=3.8 S (Gi is the conductance of corresponding resistor Ri) L1= 20 H,C1= 5×10−2 F If we select Node 4 as the reference node...
16. ### 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?
17. ### Equivalent capacitance of a system from potential difference

Homework Statement Calculate the equivalent capacity of the capacitor system between points ##x## and ##y## Homework Equations ##C=q/V## The Attempt at a Solution I'm asking about this problem because I know how to calculate ##V_x-V_y##, but I don't know how can I extract the equivalent...
18. ### Resonant circuit current calulation

hello, collegues, I need to calculate current on the right circuit, but I don't really know how. I have the current in left circuit I and L1 L2 C1 C2. I have tried to calculate this using impedance and ohms law. As Z2=Xc+XL, and U2=jwM, where M - mutual inductance I think that I2 should be...
19. ### Reading of the voltmeter with closed switch

Homework Statement (a) In the circuit shown below E is a cell of source (internal) resistance r and the resistance of R is 4.0 Ω. With the switch S open, the high resistance voltmeter reads 10.0 V and with S closed the voltmeter reads 8.0 V. Show that r = 1.0 Ω. (b) If R were replaced by a...
20. ### Thermal radiation, emissivity and Kirchhoff

Hi Guys Studying thermal radiation here and I am kinda stuck at one point Kirchhoff law states that at thermodynamical equilibrium, the amount of energy absorbed must be reemited. But before the system reaches equilibrium, is there a model to predict how much energy of these photons absorbed...
21. ### Kirchhoff's Law with Capacitors: Voltage, Resistance & Charge

Hello! I am bit confused about kirchhoffs law with capacitors. So if I have a battery and resistance, I obtain V-RI=0. But from what I read, if I have a capacitor and resistance (so discharging capacitor), the equation reads R(dq/dt) + q/c = 0, which is equivalent to RI + q/c =0. Why in this...
22. ### A Kirchhoff law for absorption and emission of a gas

Hi Guys I´m studying the absorption and emission phenomena of a gas and, according to Kirchhoff "extended" law, for a body at thermodynamic equilibrium, the following statement is true. ελ(T,θ,φ) = Aλ(T, θ,φ). So, if i understood correctly the meaning of this equation, The amount of absorbed...
23. ### Ground circuit and kirchhoff law(holiday 27.30)

Homework Statement I attatched my question as a picture Homework EquationsThe Attempt at a Solution 1.i found a solution using kirchhoff law, V1=-11V,V2=-9V and it was correct. but i`m not sure that my method was right. i know that kirchhoff law is originated from charge and energy...
24. ### I Verifying Kirchhoff formula

I've read the derivation of Kirchhoff's formula for three dimensional wave equation using the Euler-Poisson-Darboux equation. The derivation seems to be fine, but I thought that the Kirchhoff's formula as a final result is a kind of result that you should be able to verify it by substituting it...
25. ### Kirchoff's Laws Problem Current

Homework Statement Given a battery with voltage 35.7 V and 4 Resistors (Top left with resistance 2R, and the 3 others each with resistance R) where R = 507 Ohms, what current would an ideal ammeter read in its current position? (Diagram attached) Homework Equations Kirchoff's Laws: KCL and...
26. ### Kirchhoff Law Problem: Find Current and Potential Difference | Solution Included

Homework Statement https://fbcdn-photos-c-a.akamaihd.net/hphotos-ak-xft1/v/t1.0-0/s480x480/12802893_10205707400875867_4855727067132215897_n.jpg?oh=b486598e6f2016a814eb52bf48870334&oe=57648CD9&__gda__=1464637082_3cae40328f43f09eaa2cf9cf5b2f0b0f Homework Equations Kirchhoff Law 1. Find the...
27. ### Kirchoff's Loop Rule Involving 2 Resistors and a Capacitor

A 5μF capacitor is connected in parallel with a 2MΩ resistor and the combination is then connected in series with a 1MΩ resistor through a switch to a 12V battery. Find the time taken for the voltage across the capacitor to rise from zero initial value to 2V after the switch is closed.From what...
28. ### Finding current in a circuit using Kirchhoff voltage law

Homework Statement Hi, I'm learning about Kirchhoff's laws, and have to solve the circuit. Attached picture of part the circuit I am attempting to solve. The ammeter reads 2 A. Homework Equations Kirchhoff's voltage law says the total voltage around a closed loop must be zero. The Attempt at...
29. ### Determining current from ammeter

Homework Statement The ammeter reads 5.0A. Find I1, I2, and ε Homework Equations ΔV=IR The Attempt at a Solution I've never dealt with ammeters before so I'm very confused. To start, I tried breaking this into loops, and then used Kirchhoff's Law. I started with the left side, since I...
30. ### How to prove Kirchhoff's loop rule?

In common test books the "proof" is usually use an example of a simple one-loop system with battery and resistor. In such a case, the current actually goes round the loop and the same current flows throughout the loop. However in actual case, there may be different currents in different...
31. ### How do Kirchhoff's Rules apply to a circuit with multiple resistors in series?

Homework Statement [/B] Consider the circuit above. You are given the following measured values: V = 1.5 V R1 = 100 R2 = 100 R3 = 50 R4 = 50 R5 = 50 Homework Equations Kirchhoff's Loop Rule and Junction Rule The Attempt at a Solution I tried setting this up using the junction and loop...
32. ### Finding Effective Resistance using Kirchhoff's Rule

Homework Statement Find the effective resistance between the points 'x' and 'y'. When the middle Resistance is 5 ohms. Homework Equations Ohm's Law - V=IR. Kirchhoff's Junction and Loop (Mesh) Rule. The Attempt at a Solution I drew the following diagram: I got the correct answer when I...
33. ### Working around with Electric Circuitry.

Though I understand the basic combinations of resistors, emf and capacitors, both in parallel and series, complex circuitry questions always baffles me. I would like to know what are the key points? I mean important points to be kept in mind. What are the common mistakes? What are certain tricks...
34. ### Engineering Tough Circuit Problem, Find Current When Switch is Closed

Homework Statement I got questions a) and b), but I'm stuck at c) and d). Homework Equations Kirchhoff's Loop and Junction rules. Equivalent resistance in series: Req = R1 + R2 Equivalent resistance in parallel: Req = ((R1)-1 + (R2)-1)-1 The Attempt at a Solution I really haven't gotten...
35. ### MHB Current Equivalence at a Circuit Node

Given the circuit below: Why does KCL equate to $\frac{e - v_c}{R_1} = C\frac{dv_c}{dt} + f(v_c) + i_L$
36. ### Finding the current in each resistor - Kirchhoff

Homework Statement Find the current in each resistor of this circuit. Homework Equations Kirchoff's Current Law The Attempt at a Solution I just need a nudge in the right direction. I am fairly sure Kirchoff's Current Law comes into play, and have counted 6 loops and 4...
37. ### Solve Kirchhoff Problem: Find I1, I2, I3

Homework Statement Find I1, I2, I3 http://i58.tinypic.com/hwg4y0.png (Problem included in image) Homework Equations Junction Rule, Kirchhoff, Ohms Law The Attempt at a Solution I don't understand Kirchhoff at all. All i got was I2=I1+I3 and I think that might be wrong.
38. ### Kirchhoff current law question

http://postimg.org/image/mk8vo32in/ Just wondering whether the 3A from the current source should be included when writing a KCL equation for nodes a and c, and if yes, why the full 3A? Wouldn't it split up along the way thanks
39. ### Kirchhoff's Rules Homework Solution

Homework Statement Find Kirchoff's laws for this http://postimg.org/image/d78dvdg5f/ (Actual problem has a bit more but I can do that part.)Homework Equations Loop rule Junction ruleThe Attempt at a Solution I got the following equations 2e - 4i_4 - 2i_2 = 0 e - 3i_3 - i_1 = 0 e - 4i_4 -...
40. ### Kirchhoff Transform: Thermal Diffusivity Dependency?

When applying Kirchhoff's transformation to heat conduction PDE with temperature dependent thermophysical properties (k,ρ , Cp) , one obtains a transformed energy variable u=∫Cp(τ) dτ and a term for a thermal diffusivity (α=k/ρ*Cp), thus reducing the nonlinerarity of the equation. When...
41. ### Finding the magnitude and direction of current thro Kirchhoff law

Homework Statement Revered Members, Please go through my attachment. I have been asked to find the magnitude and direction of current through the 10 ohm resistor. The answer that is given in the book is 1/23 Ampere from A to B. But i solved as given in the attachment but i got the answer...
42. ### Kirchhoff Laws: Conventional Or Electron Flow

Hi, Ive trying to work through Kirchhoffs voltage and current laws. Ive so far calculated: Current in Loop one (I1): 3 Amps going anticlockwise Current in Loop Two (I2): 4 amps going anticlockwise Current in Loop Three (I3): 8 amps going anticlockwise R1: 5 amps going up = (Current...
43. ### Archived How to include resistance of wire and voltmeter in Kirchhoff equations

Homework Statement I'm doing a lab report and the last question is, how would your measurements (currents and voltages across each resistor) be affected if the resistance of the wires is 0.01 Ω and the internal resistance of the voltmeter is 10 MΩ? Homework Equations The Attempt at a...
44. ### Understanding Kirchhoff's Laws: Solving a Parallel Circuit Problem

Homework Statement my work I know part A is incorrect because for my part B my quadratic contains an imaginary,which I doubt he would due. Some help would be awesome since it is due tomorrow, and will probably be on the exam as well.
45. ### Kirchhoff Voltage Law Explanation: Derivation/Proof

hi! i understand how the krichoff current law works , but can someone explain me the derivation/proof of the voltage law .
46. ### Engineering Finding current in a RLC circuit using kirchhoff laws

Homework Statement Find current flowing through E1 ( find I1). Homework Equations I see 6 currents, atleast until the capacitor is charged, what i find confusing are the branches without any resistance and they seem to mess up my equations. The Attempt at a Solution 1st kirchhoff's law...
47. ### Need help to get equation of Kirchhoff

Please help me! I can't understand how to get equation of Kirchhoff to this scheme. Thank you! http://i5.pixs.ru/storage/4/3/0/shemaJPG_8094561_3553430.jpg
48. ### What is the correct way to pronounce Kirchhoff ?

What is the correct way to pronounce "Kirchhoff"? What is the correct way to pronounce "Kirchhoff"? I keep hearing the same two pronunciations over and over: #1 sounds like KIRK HOFF (the preferred pronunciation of the prof who instructed my E&M class) #2 sounds like KEER SHOFF Which...
49. ### Simple kirchhoff 2nd rule problem

hi everyone, please i need urgent help. in the attached image if R=1 ohm is traverse from b to H, why is potential change taken as -ive. the point H is close to +ive terminal of 5V power supply so it could also be a positive potential when traversing from b to H? please help me. hope you...
50. ### Kirchhoff's Loop Rule: Example 26.4 Explained

hi everyone this is about the example 26.4 in attached pdf. I'm having problem in conceptual understanding of kirchhoff's loop rule. I'm total beginner in physics. in the example 12v battery is used to feed the entire circuit, primarily to recharge the run-down battery. please see the...