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rudransh verma

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is a measure of “number of field lines” passing through S. I put this in quotes because of course we can only draw a representative sample of field lines. The total number would be infinite.

**But for a given sampling rate the flux is proportional to the number of field lines drawn, because the field strength, remember is proportional to the density of field lines(the number per unit area), and hence E.da is proportional to the number of field lines passing through the infinitesimal area da.**

I didn’t get it?

It’s from chapter 2 Electrostatics from

**Introduction to electrodynamics**by Griffiths.

I have read in a book that field lines number crossing is proportional to Edelta S.

I can understand that something is proportional to area but to product of field and area makes no sense.