756_Physics ProblemsTechnical Physics

# 756_Physics ProblemsTechnical Physics - 96 Capacitance and...

This preview shows page 1. Sign up to view the full content.

96 Capacitance and Dielectrics P26.58 (a) We use Equation 26.11 to find the potential energy of the capacitor. As we will see, the potential difference V changes as the dielectric is withdrawn. The initial and final energies are U Q C i i = F H G I K J 1 2 2 and U Q C f f = F H G I K J 1 2 2 . But the initial capacitance (with the dielectric) is C C i f = κ . Therefore, U Q C f i = F H G I K J 1 2 2 κ . Since the work done by the external force in removing the dielectric equals the change in potential energy, we have W U U Q C Q C Q C f i i i i = = F H G I K J F H G I K J = F H G I K J 1 2 1 2 1 2 1 2 2 2 κ κ a f . To express this relation in terms of potential difference V i , we substitute Q C V i i = b g , and evaluate: W C V i i = = × = × 1 2 1 1 2 2 00 10 100 5 00 1 00 4 00 10 2 9 2 5 b g a f e j a f a f κ . . . . F V J . The positive result confirms that the final energy of the capacitor is greater than the initial energy. The extra energy comes from the work done on
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern