This might be more of a lesson on proper probing than anything! There would be much less confusion if you have reliable results.

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Dr. Walter Lewin’s videos on Kirchhoff’s Voltage Law:

https://up-tube.com/upvideo/aTDoN2wjxJV

https://up-tube.com/upvideo/YmG_LM0kPSL

https://up-tube.com/upvideo/jm_TdB-Hex4

https://up-tube.com/upvideo/s3-FsmrchCf

By: Mehdi Sadaghdar

--------------------------------------------------------------------------0

#Kirchhoff #KVL #KCL #ElectroBOOM

It would be pretty awesome if you support ElectroBOOM at Patreon:

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Thanks to http://CircuitSpecialists.com for proving my essential lab tools and giveaways.

Below are my Super Patrons with support to the extreme!

Nicholas Moller at https://www.usbmemorydirect.com

The Guitar Rig Guru at https://www.altium.com/

Alex Bakhuizen

My sponsors and top patrons: http://www.electroboom.com/?page_id=727

Dr. Walter Lewin’s videos on Kirchhoff’s Voltage Law:

https://up-tube.com/upvideo/aTDoN2wjxJV

https://up-tube.com/upvideo/YmG_LM0kPSL

https://up-tube.com/upvideo/jm_TdB-Hex4

https://up-tube.com/upvideo/s3-FsmrchCf

By: Mehdi Sadaghdar

--------------------------------------------------------------------------0

#Kirchhoff #KVL #KCL #ElectroBOOM

## Comments 3818 Comments

Voltage between two points is defined as the work done to move a unit of charge between those two points. Kirchoff's voltage law says that if those two points are the same point, the work done is zero. For the the electron to do work in a light bulb, it must have work done to it by, say, a battery.

Now imagine Kirchoff's law holds. Imagine any arbitrary path between two points, P1 and P2. We can form a closed loop with a direct path from P2 back to P1. If Kirchoff's voltage law holds, then the voltage from P1 to P2 along the arbitrary path must equal the negative of the voltage from P2 to P1 along the direct path. Since the voltage from P2 to P1 along the direct path is a constant, the voltage from P1 to P2 along the arbitrary path must be a constant as well. In other words, Kirchoff's voltage law is precisely equivalent to saying the electric field is path independent.

Kirchoff's voltage law is true if, and only if, the electric field is path independent because it says the voltage difference between two points along any path must equal the negative of the voltage difference between those two points on a direct path.

Unfortunately, it now gets complicated. But I will point you to two very clear sources that explain that the electric field is path independent if, and only if, the magnetic field is constant and that motors and generators work precisely because a changing magnetic field makes the electric field path dependent:

https://en.wikipedia.org/wiki/Electric_potential#Generalization_to_electrodynamics

https://en.wikipedia.org/wiki/Faraday%27s_law_of_induction

"The most widespread version of Faraday's law states: The electromotive force around a closed path is equal to the negative of the time rate of change of the magnetic flux enclosed by the path."

In other words, Kirchoff's voltage law says that the EMF around a closed path is zero and Faraday's law -- the way induction works -- says that it is non-zero. They cannot both be right.

To agree with Mehdi, you would also have to disagree with this statement, "The Maxwell–Faraday equation states that a time-varying magnetic field will always accompany a spatially varying, non-conservative electric field, and vice versa." A path-independent field is conservative, and the Maxwell-Faraday equation states that a time-varying magnetic field makes the electric field non-conservative and thus path-dependent. As shown above, a path-dependent electric field violates Kirchoff's voltage law. So you cannot have both the Maxwell-Faraday equation true and Kirchoff's voltage law true if the magnetic field is time varying.

Martin lewis versus Electroboom

Maybe there is no absolutely right or wrong at here.But the divergence between scientist and engineer.

but on the less delusional side -> Blackbody Radiation, Planck's Law, and Kirchhoff's [fallacy]:

https://up-tube.com/channel/HPY7DVBMgrJCcOJOBy8v0r-t/cynlyvfgf

your Mum doesn't understand you either !

: )

Pls

I believe the professor was simply highlighting this misunderstanding. By showing us a circuit where the change in flux of the loop is not zero. So he's not showing us that Kirchoffs rules are wrong per se. He's merely highlighting that condition that most of us tend to forget since it's pretty rare to come across it in real life.

Edit.

You must remember that even if a number of different possible solutions exist where Kirchoffs rule is applicable. (Such as your examples in the latter half of the video) Just one where it is not is sufficient to prove it's not an absolute law. I don't believe there were any real errors in your circuiting the first time right ? If that's true then I believe you successfully proved yourself that Kirchoffs rules do not always hold !

https://up-tube.com/upvideo/-NwqHhd8WAL&yp=m233w5dn4lojvupx2npqc430vb3art0fha3diuqfi3qj03p010p.1542275756062948