Ring of radius R and uniform charge

  • Thread starter arl146
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Homework Statement


At what distance along the central axis of a ring of radius R = 0.200 m and uniform charge is the magnitude of the electric field due to the ring's charge maximum? What is the positive solution for z?


Homework Equations


E = [itex]\frac{kqz}{(z^2+R^2)^(3/2)}[/itex]



The Attempt at a Solution


I know I should differentiate that above equation with respect to z and then set it equal to 0 to get z but i just dont know how to differentiate that ..

E = [itex]\frac{kqz}{(z^2+R^2)^(3/2)}[/itex]

the k and the q are held as constants and can be taken out of the differentiation ..

= kq*[[itex]\frac{d}{dz}[/itex]((z2+R2)3/2]

isn't [itex]\frac{d}{dz}[/itex]((z2+R2)3/2 = -3z(z2+R2)^(-5/2) ??

so it would be kq [-3z(z2+R2)^(-5/2)]

but that doesn't work for when you set it = 0. what am i supposed to be doing that im not
 

Answers and Replies

  • #2
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never mind .. i got it now!
 

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