EK. No. 148...If the distance between a point charge and an infinitely large charged plate is increased b a factor of 2, the new force on the point charge will:
C. remain the same.
C. remain the same.
F b/w charge & infinetely large charged plate
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This is a really good question.. How come the force on a charged particle in an electric field is independent of distance but the force on 2 charged particles is dependent on the square of the distance between them?
EDIT: is the answer in the word "Infinite"? F=k(q1*q2)/r^2 if one of your charges is infinitely large then it doesn't matter how far they are apart.
EDIT: is the answer in the word "Infinite"? F=k(q1*q2)/r^2 if one of your charges is infinitely large then it doesn't matter how far they are apart.
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The electric field created by an infinite plane is uniform with strength σ/(2ε0). You can derive that from the formula for the electric field for a disk and take the limit when the radius of the disk goes to infinity. There was also a neat way to do it using Gauss'es law but I can't remember exactly how it was done - I can look it up if you really want. For MCAT purposes I think you'll be safe taking it as a fact.
Trying to visualize that as a concept might be a bit harder. One way to think about it is that the plane is infinite and uniform, so you have no sense of scale as you move further or closer to it. But in general trying to visualize infinity tends to be non-trivial.
Trying to visualize that as a concept might be a bit harder. One way to think about it is that the plane is infinite and uniform, so you have no sense of scale as you move further or closer to it. But in general trying to visualize infinity tends to be non-trivial.
Ok, just saw Khan's proof on why the electric field of an infinitely charged plate is uniform in strength- and thus why force felt by charge is also constant across different distances from the plate.
After lots of calc, he concluded that electric field of infinite plate, E= 2kπ(charge density).
So the only variable that will change the electric field of an infinitely charge plate is a change in "charge density" --the electric charge per unit area.
After lots of calc, he concluded that electric field of infinite plate, E= 2kπ(charge density).
So the only variable that will change the electric field of an infinitely charge plate is a change in "charge density" --the electric charge per unit area.
