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## Homework Statement

What is the electric potential a distance x above the center of a ring of charge Q with a

radius R? Derive the electric field from this relationship.

## Homework Equations

V=k_e[tex]\int[/tex]dq/r = k_e[tex]\int[/tex]dq/([tex]\sqrt{}[/tex]a^2+x^2)

## The Attempt at a Solution

V= k_e/([tex]\sqrt{}[/tex]a^2+x^2)[tex]\int[/tex] dq=k_eQ/([tex]\sqrt{}[/tex]a^2+x^2)

E_x=-dV/dx= -k_eQ(d/dx)(a^2+x^2)^-1/2

= -k_e(-1/2)(a^2+x^2)^-3/2(2x)

E_x= k_ex/(a^2+x^2)^3/2 Q

Is this right? If not what is?