Qu:
The two protons of a helium nucleus are about
apart. Find the electrostatic force between them. How much work must be done against this force in bringing two protons from infinity to this separation?
Ok, here's what I've done so far:
Electrostatic force =
(3 sf)
Now, the second part concerns the work done, given by
which gives:
I took half the distance since the question said between the two protons. But my book says the answer is 1.5x10^-13... :(
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Now, another one.
A capacitor is connected from two concentric spheres, the inner sphere being positively charged and the outer sphere being earthed.
Draw three sketch diagrams, using the same scales, to show how the electric field E(r) due to:
a) the charges on the inner sphere alone
b) the charges on the outer sphere alone
c) the charges of all charges
varies with distance r from the centre.
I got my first two graphs similar to the graphs of y = k/x, and both have are similar. I took both fields as positive since they are in the same direction.
For the third one, all I see is that if the radius r is the same, then the electric field will cancel out, hence, the electric field is zero. Is that a correct assumption?