LECT6_1661610

LECT6_1661610 - 2 Charged Planes Equipotential surfaces are...

This preview shows pages 1–16. Sign up to view the full content.

2 Charged Planes Equipotential surfaces are parallel to the planes and to the E-field lines

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

View Full Document
Capactitors & Capacitance Capacitor: a device for storing electrical potential energy Can also be rapidly discharged to release a large amount of energy at once Applications: camera flashes, automobile ignition systems, computer memory, laser flash lamps, defibrillators
Laser Fusion at the Nat’l Ignition Facility, Livermore, CA. 10 6 J released in μ s: Power ~ 10 12 W Credit:: LLNL

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

View Full Document
A Capacitor Capacitance is defined as the ability to store separated charge. C = Q / Δ V Unit: FARAD = C/V Note: +Q plate is connected to positive terminal of battery; –Q plate connected to – terminal.

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

View Full Document
Parallel Plate Capacitor Note E-field inside is pretty uniform. E-field outside is relatively negligible Charges like to accumulate at inner edges of plates + + + + + + + + + + + + + + + + + + + + + + + + + + + + + - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Parallel Plate Capacitor Capacitance depends on geometry: C = ε 0 A / d

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

View Full Document
Variable capacitor: C depends on “overlapping” area
E = σ / ε 0 = (q/A)/ ε 0 = Δ V/d single sheet of charge +Q: E = σ /(2 ε 0 ) +Q –Q Parallel plate capac.:

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

View Full Document
A 2A: C = ε 0 A/d C 2C Double the area…
Δ V Δ V (held constant) d d/2 What happens to C & E? If plates are HELD at a fixed potential difference Δ V which does not change as you decrease d: + - + -

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

View Full Document
Δ V Δ V (held constant) d d/2 E = Δ V/d so E 2E E = σ / ε 0 = (Q/A)/ ε 0 so Q 2Q C = Q/ Δ V so C 2C If plates are HELD at a fixed potential difference Δ V which does not change as you decrease d: + - + -
Capacitors with insulators (for small d) With insulating material filling the gap, charges cannot travel from one plate to the other, but E- fields can permeate.

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

View Full Document
A parallel-plate capacitor with A = 4 cm 2 , d = 1 mm. Find its capacitance. C = ε o A/d = (8.85x10 -12 C 2 /Nm 2 )(4x10 -4 m 2 )/(10 -3 m) = 3.54x10 -12 F = 3.54pF If the capacitor is connected to a 9 Volt battery, how much charge is on each plate? C = Q/ Δ V Q = C Δ V = (3.54x10 -12 F)(9V) =3.2x10 -11 C Example:
Calculate the magnitude of the E-field inside the capacitor.

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

View Full Document
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