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Dec4-10, 12:14 PM
P: 17,506
Quote Quote by cabraham View Post
Prof. Lewin is right. KVL is a conditional law based on conditions that no time changing mag fields are present. It holds when this condition is met. KVL is not a universal law.
You are partly correct. KVL is indeed an approximation to Maxwell's equations based on the assumptions of circuit theory which are, as follows:
1) the circuit is small relative to the wavelengths involved (lumped-parameter system)
2) no net charge on any component at any time
3) no magnetic coupling between components

You can have changing magnetic fields within a component (e.g. in an inductor) as long as there is no magnetic coupling between components.