1 / 17

Electrostatic Forces

Electrostatic Forces. Gravitational vs. Electrostatic Coulomb’s Law Coulomb’s Law Examples The Electric Field Electric Field Examples Continuous/constant Electric Fields Constant Field Examples. Gravitational vs. Electrostatic. Examples of Coulomb’s Law I. Example 16-1

majed
Download Presentation

Electrostatic Forces

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Electrostatic Forces • Gravitational vs. Electrostatic • Coulomb’s Law • Coulomb’s Law Examples • The Electric Field • Electric Field Examples • Continuous/constant Electric Fields • Constant Field Examples

  2. Gravitational vs. Electrostatic

  3. Examples of Coulomb’s Law I • Example 16-1 • Example 16-3 (1D vector addition)

  4. Examples of Coulomb’s Law II • Example 16-4 (2D vector addition) • Problem 13 (Charge Triangle)

  5. A Gravitational “Field” • All falling objects have a = 9.8 m/s2 down (early Sep) • Plug into velocity and displacement equations • All objects have “weight” mg down (late Sep) • Plug into F= ma, get a = 9.8 m/s2 down, v, x • Two objects attract according to F=GMm/r2 (early Oct) • Near Earth’s surface GM/r2 = 9.8 m/s2 down • Just multiply by mass • Most of the problem calculated “ahead of time” • GM/r2 can be considered “field” (now) • GM/r2 varies with altitude (< 9.8 m/s2) • Direction still down • Units acceleration (m/s2) or Force/mass (N/kg) • Multiply mass by “Vector field”

  6. Electric Field • In gravitation we calculated • Bracket part usually became “g” • Since a = 9.8 m/s2 => F = ma = mg • Also interpret g = Force/mass units N/kg • Gravitational “field” • Allows us to pre-calculate most of problem • Same with electrostatics

  7. Electric Field

  8. Examples of Electric Field • Example 16-8 • Example 16-9

  9. Continuous charge distributions • Field due to discrete charge • Field due to line of charge • Field due to ring of charge • Field due to sheet of charge • Coulomb’s Law plus a lot of integral calculus! (and we’ll just give you results)

  10. Line of Charge

  11. Ring of Charge

  12. Sheet of Charge

  13. Continuous charge distributions - Summary

  14. Continuous charge - Constant Electric Field These problems all assume a constant electric field in some region (like between two conducting sheets of charge). • Example 16-6 • Problem 23 • Problem 24 • Problem 27 • Problem 31

  15. Field Lines • Point in direction of electric field – Direction positive charge will move, opposite direction negative charge will move. • F = qE • Density is proportional to field strength - E proportional to lines/area. • Begin on positive, end on negative – In between field lines continuous. • Examples page 455.

  16. Gauss’s Law • Net number of field lines entering or leaving proportional to charge enclosed. ∫E dA = Qenc/εo εo = 1/4πk = 8.85 * 10-12 C2/Nm2 • Note • Surface must be closed surface • Field must be perpendicular to surface • Need symmetry to evaluate

  17. Gauss’s Law Examples • Point charge • Line of charge • Sheet of charge

More Related