[SOLVED] Faraday's law and RC circuits

[joao_lima]

Hey,

I am trying to understand an statement made in another post but thought it would be better to start a new thread.

In accordance to Faraday's law is stated that the magnetic flux in a transformers core is proportional to the integral of the applied voltage in the inputs of the transformer. In order to measure this integral it is suggested to use a integrator RC in series circuit over the inputs of the transformer, the reason as stated was that the voltage over the capacitor would be the integral of the voltage over the series RC circuit, therefore the same integral of the voltage in the Faraday's law applied in the transformer.

I don't know if I got it wrong at some point, and this statements might be wrong, but if they are right can someone explain me why this is true?

Regards

joao_lima

This is the link to the original post:
https://www.edaboard.com/threads/302652/#post1296139

Post number 22

 

[FvM]

Two points should be clarified:

- the transformer input voltage is not exactly equal to the flux generating or induced voltage. It has to be reduced by the resistive voltage drop of the winding.
- the capacitor voltage is approximately proportional to the RC input voltage integral only if V(C) << V(R).

 

[joao_lima]

Two points should be clarified:

- the transformer input voltage is not exactly equal to the flux generating or induced voltage. It has to be reduced by the resistive voltage drop of the winding.
- the capacitor voltage is approximately proportional to the RC input voltage integral only if V(C) << V(R).

I can't understand mathematically how the capacitor voltage is approximately proportional to he RC input voltage integral, can you clarify that for me?

Regards,

João

 

[godfreyl]

By definition, the voltage across a capacitor is proportional to the integral of the current flowing through it. Also, the current through a resistor is proportional to the voltage across it.

Thus, in a series RC circuit, the voltage across the capacitor is proportional to the integral of the voltage across the resistor.