q3s - Physics 2212 K Summer 2009 Quiz #3 Solutions...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Quiz #3 Solutions Summer 2009 ² 0 Permittivity constant m p Mass of a proton μ 0 Permeability constant m e Mass of an electron e Fundamental charge c Speed of light K Coulomb constant g Acceleration due to gravity Unless otherwise directed, friction, drag, and gravity should be neglected, and all batteries and wires are ideal. Any integrals in free-response problems must be evaluated. I . (24 points) The circuit illustrated has an emf E , and six capacitors, each with capacitance C . What is the potential energy stored in the capacitor at the upper right, marked with an asterisk ( * )? Express your answer in terms of parameters defined in the problem, and phys- ical or mathematical constants. (Let the potential energy stored in an uncharged capacitor be zero.) . . . . . . . . . . . . . . . If the charge on or potential across the asterisked capacitor can be found, then the energy stored in it can be determined. The equivalent capacitance of the circuit should be calculated. The three capacitors circled in red are in series. Their equivalent capacitance is C red = ± 1 C + 1 C + 1 C - 1 = ± 3 C - 1 = C/ 3 Redrawing the circuit with that combination, one can see that the three capacitors circled in blue are in parallel. Their equivalent capacitance is C blue = C + C + C/ 3 = 7 C/ 3 Redrawing the circuit with that combination, one can see that the aster- isked capacitor is in series with all the rest. The equivalent capacitance of the circuit is C eq = ± 1 7 C/ 3 + 1 C - 1 = ± 3 7 C + 7 7 C - 1 = ± 10 7 C - 1 = 7 C/ 10 The charge delivered by the battery is Q = C eq Δ V = ± 7 C 10 E and since the asterisked capacitor is in series with all the rest, this must also be the charge on it. Therefore, the energy stored in the asterisked capacitor is U = Q 2 2 C = ( 7 C 10 E ) 2 2 C
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 05/08/2010 for the course PHYS 2212 taught by Professor Kindermann during the Summer '09 term at Georgia Institute of Technology.

Page1 / 4

q3s - Physics 2212 K Summer 2009 Quiz #3 Solutions...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online