Two particles, with charges of 50.0 nC and -50.0 nC, are placed at the points wi
ID: 2168750 • Letter: T
Question
Two particles, with charges of 50.0 nC and -50.0 nC, are placed at the points with coordinates (0, 8.00) cm and (0, -8.00) cm as shown below. A particle with charge 25.0 nC is located at the origin.
Explanation / Answer
Alright, so the potential of a configuration is the sum of the potentials between each charge. The expression for each charge is V=kq1q2/r. So, naming the charges from top to bottom q1, q2, q3, and let's use q=25 nc, r=8 cm. The expression for total potential is:
(2kq^2/r)+(-2kq^2/r)+(-4kq^2/2r)
Simplifying,
-2kq^2/r
Well, that's nice, 2 of those expressions cancel each other out. Plugging in numbers (and remember to use the right units):
-2(8.8976E9 m/F)*(25E-9 C)^2/(8E-2 m) = -1.38E-4 J
Or, -139 microJoules. (note: I use E to mean x10^. It's a scientific notation thing)
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