Why Electric Flux \Phi is Defined

AI Thread Summary
Electric flux \Phi is defined as EAcos\theta to represent the projection of the electric field E through a surface area A. The cosine factor accounts for the angle \theta between the electric field and the normal to the surface, affecting the amount of field passing through. This concept is similar to counting the number of bugs hitting a tilted windscreen, where the impact decreases as the angle increases. The mathematical representation of flux involves the dot product of the electric field and the differential area vector. Understanding this definition is crucial for applying Gauss's law in physics.
yaik
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Why the electric flux \Phi is defined as EAcos\theta?

I don't understand the part about cos\theta...
 
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Welcome to PF!

Hi yaik! Welcome to PF! :smile:

Imagine you want to know the flux of bugs flying horizontally along a road.

If you count the number that go splat on your windscreen, then you'll collect less (in a given time) if the windscreen is tilted: the number will be greatest at 90º, and zero at 0º: it'll be proportional to cosθ. :smile:

Mathematically, flux of a field E through a surface with area A is E.(Añ), where ñ is the unit vector normal (perpendicular) to the surface. :wink:​
 
thx!
 

Thread 'Why measure the speed of light in one direction?'

It may be shown from the equations of electromagnetism, by James Clerk Maxwell in the 1860’s, that the speed of light in the vacuum of free space is related to electric permittivity (ϵ) and magnetic permeability (μ) by the equation: c=1/√( μ ϵ ) . This value is a constant for the vacuum of free space and is independent of the motion of the observer. It was this fact, in part, that led Albert Einstein to Special Relativity.
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