Electric potential of insulating rod

[pattiecake]

This hmwk. problem has got me totally buggin...

A uniformly charged insulating rod of length 20cm is bent into the shape of a semicircle (so it looks like the letter "C"). The rod has a total charge of -8.50e-6C. Find the electric potential at a point P, in the center of the semicircle.

I know crazy things happen to electric potential when dealing with insulators...also, will this problem involve integrals?

If anyone has a clue I'd appreciate the guidance! Thanks in advance!

 

[pattiecake]

Why will no one respond? =(

 

[paul11273]

Yes, this requires and integral.

$$V=ke \int{dq/r}$$
$$V =ke(Q/r)$$

Where Q is the total charge of the rod and r is the radius this rod makes. Remember that circumference=2*pi*r, so use that to find r.

When you figure it out, post your answer.

I think no one has responded because you didn't post any sort of work that you did.
Post up what you have and we can take this further.

 

[pattiecake]

thank u so much. i didn't mean to be an answer leech!

i used this formula before: V=Ke(Q/r): using Circumference=2piR to find the radius. The problem was after i got my answer: -2.39, i forgot we were dealing with a semicircle, and that i had to divide by 2. my final answer (which webassign confirmed) was -1.2MV. thanks so much for your help!