Calculate the amount of work required to assemble a system of charges.

[ditde]

Homework Statement

The three charges shown below (Q1=22.6*10^-6C, Q2=22.6*10^-6C, Q3=61.0*10^-6C) are at the corners of an iscoceles triangle with sides a=4 m and b=2 m.

Q3 is 2m from Q1 and Q2, Q1 is 4m from Q2. In other words, Q3 is the point charge at the "tip" of the isosceles triangle.

Calculate the amount of work required to assemble this system of charges, assuming they are brought in from infinity.

Homework Equations

W = ΔPE = qΔV = q(Vi-Vf)
V = kQ/r

Being brought in from infinity means that Vi (initial voltage) = 0.

The Attempt at a Solution

I calculated the work required to bring in each charge individually and attempted to add them in the end.

Example of my working;

Work1 = Q1 * (0 - Vf)

Vf = kQ2/r2 + kQ3/r3

Work1 = 22.6*10^-6 * (0-(((9.10^9*22.6*10^-6)/4)+((9.10^9*61.0*10^-6)/2))

 

[mfb]

I calculated the work required to bring in each charge individually and attempted to add them in the end.

That is fine.
Try to work with units please, it is easier to find errors that way.