Does Kirchhoff's Law Hold? Disagreeing with a Master

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Cites Hey Hey · 2018-11 · Electrical Engineering Stack Exchange · on “Does this experiment show that Kirchhoff's Law hold when there's a changing magnetic field involved in a circuit?”

In this video [this video] , the electrical engineer and youtuber Mehdi Sadaghdar (ElectroBOOM) disagrees with another video [LINK] from professor Walter Lewin. Basically, professor Lewin shows in an experiment that if we have two different resistances connected in a closed loop, and if we generate a changing magnetic field using a coil, the voltage at the endpoints of the two resistances will be different, contrary to the expectations from Kirchhoff's Voltage Law (KVL). simulate this circuit [LINK] – Schematic created using CircuitLab [LINK] According to the experiment, the left voltmeter VM1 shows a voltage different from the second voltmeter VM2. Lewin then concludes that KVL does not hold whe

Cites Math Keeps Me Busy · 2021-01 · Electrical Engineering Stack Exchange · on “Primary voltage drop in current transformer”

Would we see a larger reading on VM2 compared with VM1 (10 mm and 5 mm from the plane of the CT, for example)? Unlikely. Each volt-meter together with its leads and corresponding section of the wire passing through the core form a loop. That loop is cut by the varying magnetic field inside the core of the CT. Thus, they form a one loop secondary of the transformer, and will see a voltage almost identical to the voltage drop of the primary. Almost all of the magnetic field is confined to the core, so the area of the loop will have little effect, although theoretically, if the loop for vm2 encloses that for vm1, it might encircle more magnetic lines of force. Where does the voltage drop occur?

Cites Clemens Bartholdy · 2021-03 · Electrical Engineering Stack Exchange · on “Assigning a notion of voltage even when there is a changing magnetic field”

In Walter Lewin's lecture, he finds depending on how you keep the lead of the voltmeter for a circuit in a changing magnetic field, you will measure different values]. This experiment is discussed from 49:34 of this lecture [LINK] and then infers that this is why a notion of voltage is no longer possible in the case of changing magnetic field. According to Mr.Boom, Lewin's result had a correct result, given his setup, but his conclusion was incorrect. To demonstrate this Mr.Boom experiments ( see from 7:24 of this video before disagreeing [this video] ), where he creates a modified version where Lewin's concluded principle must be equally applicable, however in Mr. Boom's equivalent experiment, L

Cites Math Keeps Me Busy · 2024-09 · Electrical Engineering Stack Exchange · on “Assigning a notion of voltage even when there is a changing magnetic field”

Can we [assign] a notion of voltage even when there is a changing magnetic field[?] Yes (see note 1). A reasonable notion of voltage would be single valued at any given point. In cases where the curl of the (total) electric field \$\vec{E}\$ is \$\vec{0}\$ , i.e. \$\nabla\times\vec{E}=\vec{0}\$ , within a simply connected region of space, we can define a potential function using the equation \$-\nabla\phi=\vec{E}\$ . The voltage between any two points, \$A\$ and \$B\$ is then just the difference between the values of \$\phi\$ at those two points. $$V_{ab} = \phi_b -\phi_a$$ However, there is a more general method that can be used even when \$\nabla\times\vec{E}\ne \vec{0}\$ . By Helmholtz's