## Mastering Physics Solutions: Electric Potential Energy of Three Point Charges

Electric Potential Energy of Three Point Charges

Part A = 9.11*10−2 J

Solution Below:

Part A

Three equal point charges, each with charge 1.30 μC, are placed at the vertices of an equilateral triangle whose sides are of length 0.500 m. What is the electric potential energy U of the system? (Take as zero the potential energy of the three charges when they are infinitely far apart.)
Use ε0 = 8.85×10−12 C2/(N*m2) for the permittivity of free space.

Mastering Physics says to use ε0 but we don’t have to (we can just use k directly). The formula to find the potential energy between two charges is:

U = (k*q1*q2)/r

And since there are 3 pairs of charges (1-2, 1-3, and 2-3), we can solve for the potential energy of the system if we multiply the above by 3 (k is the Coulomb constant, which equal’s 8.99*109N*m2/C2). Note that each charge is 1.3 μC, which equals 1.3*10-6C:

U = 3*(k*q1*q2)/r
U = 3*((8.99*109)*(1.3*10-6)*(1.3*10-6))/0.5
U = 9.11*10-2 J

9.11*10-2 J

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### 6 Responses to Mastering Physics Solutions: Electric Potential Energy of Three Point Charges

1. Erica says:

Finding this website was like seeing the light at the end of a long, dark and tumultuous storm. I could weep with sheer relief and joy at seeing this problem explained so simply and succinctly that I could understand the processes needed to obtain the answer. Thank you, Mastering Physics Solutions, for guiding me on my homework journey.

• Mastering Physics Solutions says:

Thank you very much! We are glad to help!

We think programs like Mastering Physics can be useful, but only with proper guidance and help. So we do our best to provide just that! Thank you again for your kind words!

2. Anonymous says:

the coulomb’s constant (k)suppose to be 8.99*10^9N*m2/C2, not 8.99*10-9N*m2/C2.

• Mastering Physics Solutions says:

Thank you for the good catch!

3. Francis says:

cool!!! thanks

• Mastering Physics Solutions says:

You’re welcome!