Giancoli's Physics: Principles with Applications, 6th Edition
17
Electric Potential
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17-1 to 17-4: Electric Potential
17-5: Potential Due to Point Charges
17-6: Electric Dipoles
17-7: Capacitance
17-8: Dielectrics
17-9: Electric Energy Storage
17-10: Cathode Ray Tube

Problem 16
A
$2.5 \textrm{ J}$
COMMENTS
By thesouthportschool on Wed, 2/10/2016 - 12:24 AM

How come the work is positive and not negative?

By thesouthportschool on Mon, 9/4/2017 - 9:54 AM

no one knows

By Mr. Dychko on Tue, 9/5/2017 - 3:59 AM

Hi thesouthportschool, the negative sign in $W= -qV$ that you're used to seeing is the work done by the electric field. Since, in this question, we're asked to find the work done by an external force, the external force is applying a force in the opposite direction to that of the electric field. For this reason the work done by the external force has a sign opposite to that of the electric field, which means $W_{ext} = qV$ with no negative sign.

Hope that helps,
Mr. Dychko

By william.lockhart.92 on Sun, 1/17/2021 - 10:17 PM

Why is the potential energy not 0 when the charge is midpoint between the two 35μC charges? Is it not at static equilibrium?

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