Work on Electricity (is this right?)

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The discussion focuses on calculating the work required to assemble four identical point charges of +4.0 mC at the corners of a square with 20-cm sides. The proposed formula for potential energy is U=K(q1q2/r12 + q1q3/r13 + q1q4/r14 + q2q3/r23 + q2q4/r24 + q3q4/r34). The user arrived at an answer of 3.9 but was advised to include units in their final answer. Overall, the approach to the problem is considered reasonable.
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Homework Statement


Four identical point charges (+4.0 mC) are placed at the
corners of a square which has 20-cm sides. How much work is required to
assemble this charge arrangement starting with each of the charges a very large
distance from any of the other charges?

The Attempt at a Solution


I want to know if this is the right formula and answer:

U=K(q1q2/r12 + q1q3/r13 + q1q4/r14 + q2q3/r23 + q2q4/r24 + q3q4/r34)
i got 3.9 as the answer.
 
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GlobalDuty said:

Homework Statement


Four identical point charges (+4.0 mC) are placed at the
corners of a square which has 20-cm sides. How much work is required to
assemble this charge arrangement starting with each of the charges a very large
distance from any of the other charges?


The Attempt at a Solution


I want to know if this is the right formula and answer:

U=K(q1q2/r12 + q1q3/r13 + q1q4/r14 + q2q3/r23 + q2q4/r24 + q3q4/r34)
i got 3.9 as the answer.

Looks like a reasonable approach to me. You should get in the habit of putting units on at least the answer, though.
 

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