Lecture 15-R mar4 - Lecture 15-R Review Chapters 24-27 Exam...

Info icon This preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon
Lecture 15-R Review Chapters 24-27 Exam 2 Thursday March 6 at 8:00 pm, same location No books, no electronic communications Pencils, 2 formula cards, calculator, Student ID
Image of page 1

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

View Full Document Right Arrow Icon
Thee Fundamental Capacitor (parallel plate capacitor) ch24 Question 1 The electric field between the plates is (neglect edge effects): 1. Q/(2Aε 0 ) 2. Q/(Aε 0 ) 3. 0 Answer: By superposition or realizing E = σ c 0 = Q/(Aε 0 ) and is ~uniform. Then ΔV = V = Ed = Qd/(Aε ) ►►►► C = Q/V = ε 0 A/d = C parallel plate
Image of page 2
Question 3 A 4 μF cap is charged with a 10V battery ►► Q 4 = 40 μC A 1 μF cap is charged with a 20V battery ►► Q 1 = 20 μC Caps are connected in parallel with + to - and – to + terminals together Considering C eq and the total charge separated Q total WHAT IS THE FINAL V on the “parallel” combination? 1. 20 V 2. 16 V 3. 12 V 4. 8 V 5. 4 V What are Q 4 and Q 1 after connection? 16 μC and 4 μC respectively, the charge has redistributed itself to produce 4 V on each capacitor + to + + to -
Image of page 3

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

View Full Document Right Arrow Icon
Energy “stored” in a capacitor (Demo: The “Killer Capacitor”) Separating + from - charge requires work by an external force: Moving charge Q through ΔV =V requires ΔU = W ext = QV (NOT HERE!) (This is indeed the work done by the battery!) But V of capacitor builds up as q builds up: V = q/C Thus, dU = Vdq = dW ext = (q/C)dq 2 2 0 2 0 2 1 2 1 2 1 2 1 CV QV C Q C q C qdq U Q Q q = = = = = = So why the factor of ½ here??? Question #1>>>>>
Image of page 4
Question #1 The work done by the battery to transfer Q from one conductor of the capacitor to the other is QV. The energy stored in the capacitor is only (½)QV. So what happened to the other (1/2)QV of energy? 1. Light generated while charging 2. Heating of the connecting wires 3. Energy is not conserved for moving charges 4. It went into dark energy of the universe 5. Kinetic energy of the capacitor
Image of page 5

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

View Full Document Right Arrow Icon
Dielectrics (insulators)…..so what? Separate and insulate conductors Higher dielectric strength—higher E before breakdown Increases C !! How??
Image of page 6
Image of page 7
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    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.

    Student Picture

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

  • Left Quote Icon

    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.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    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.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern