(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

I need to prove that the formula for electric potential (V) of a charged disc (with radius r) and with a uniform charge density, that

V=2kpisigma\(sqrt{x^2+r^2}-x)

when x is very large compared to r, and Q is the total charge of the disk, that this formula reduces to V=kQ/x

2. Relevant equations

Shown above

3. The attempt at a solution

I tried multiplying by a fraction of (sqrt{x^2+r^2}+x) as both numer and denom, and worked through it to get V=2kpisigma(4xsqrt{x^2+r^2})/(sqrt{x^2+r^2}+x)

Here I assumed that all under the square root was approaching x, so simplified as

V=kpisigma4x^2/x

But now I don't know if I've been doing this right..

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# Homework Help: Formula for electric potential

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