Register to reply

4 charges, find potential

by jehan60188
Tags: charges, potential
Share this thread:
Feb1-12, 03:33 PM
P: 204
1. The problem statement, all variables and given/known data

4 charges, distributed as follows

12*10[itex]^{-6}[/itex] C @ (-4,4)
12*10[itex]^{-6}[/itex] C @ (4,4)
-6*10[itex]^{-6}[/itex] C @ (-4,-4)
-3*10[itex]^{-6}[/itex] C @ (4,-4)

Calculate the potential at the origin if the potential at infinity is zero.

2. Relevant equations

V= U/q = -W/q = ∫E*dl = k*q/r

for multiple point charges, find V for each one, and sum them up

3. The attempt at a solution

[itex]V1 = V2 = \frac{k*12*10^{-6}}{(4*\sqrt{2}/2)} [/itex]
[itex]V3 = \frac{k*-6*10^{-6}}{(4*\sqrt{2}/2)} [/itex]
[itex]V4 = \frac{k*-3*10^{-6}}{(4*\sqrt{2}/2)} [/itex]

[itex]V1+V2+V3+V4 = \frac{k*3*10^{-6}}{4*\frac{\sqrt{2}}{2}}*(4+4-2-1) = 47676.7

So, I factor out the k, the 3*10e-6, and the 1/(r) from each Vi, then multiply it by 4+4-2-1 =5

this answer is not right. Any pointers?

Phys.Org News Partner Science news on
Scientists develop 'electronic nose' for rapid detection of C. diff infection
Why plants in the office make us more productive
Tesla Motors dealing as states play factory poker
Feb1-12, 03:47 PM
Sci Advisor
HW Helper
tiny-tim's Avatar
P: 26,148
hi jehan60188!
shouldn't r be 4√2 ?
Feb1-12, 05:46 PM
P: 204
Quote Quote by tiny-tim View Post
hi jehan60188!
shouldn't r be 4√2 ?

4^2 + 4^2 = 32 = 4 Sqrt(2)
why, WHY did I divide by 2?!

divided my solution by 2 (since it was sqrt(2)/2 in the divisor), and got the right answer! thanks!

mods, please feel free to close topic

Register to reply

Related Discussions
Potential at a point due to two charges Introductory Physics Homework 3
Two Charges, Find Spot of Zero Potential Introductory Physics Homework 1
Potential from two charges Introductory Physics Homework 1
Find potential energy of system with 3 charges Introductory Physics Homework 7
Point charges and potential Introductory Physics Homework 2