# Linits to Kirchoff's law

Discussion in 'General Electronics Chat' started by rag, Nov 28, 2006.

1. ### rag Thread Starter New Member

Nov 26, 2006
2
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can anybody help let me know what are the limitations of Kirchoff's law

beenthere

2. ### Dave Retired Moderator

Nov 17, 2003
6,960
145
Kirchhoff's Laws can be directly derived from Maxwell's Equations, so it should be no surprise that some imitations are those as imposed by Maxwell's Equations (why shouldn't they be?).

I cannot see a limitation of Kirchhoff's Current Law (KCL), since it takes account of both the conduction and displacement currents in Ampere's Law (please prove me wrong if I have misinterpreted this).

There is a limitation of Kirchhoff's Voltage Law (KVL) in the presence of a changing magnetic field, which from Faraday's Law implies a changing electric field which for a closed-loop is not conservative, hence the line integral of the electric field is not zero which is inconsistent with KVL (refer to the integral form of Faraday's Law for an easy way to visualise this idea: ∫E.dl ≠ 0). Additionally, there are issues with the transfer of energy from the magnetic field to the electric field for which a fudge has to be introduced to KVL to make the potential differences around the circuit equal to zero.

Dave

3. ### sci-3d Well-Known Member

Aug 22, 2006
51
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The only limitation I found of this technique is the number equations. If the circuit is complicated this lead to many equations to solve.