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COULOMB ’ S LAW, E FIELDS

COULOMB ’ S LAW, E FIELDS. Class Activities Coulomb ’ s Law. Class Activities: Charge Distibutions. Two charges +Q and -Q are fixed a distance r apart. The direction of the force on a test charge -q at A is…. Up Down Left Right Some other direction, or F =0.

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COULOMB ’ S LAW, E FIELDS

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  1. COULOMB’S LAW, E FIELDS

  2. Class ActivitiesCoulomb’s Law

  3. Class Activities: Charge Distibutions

  4. Two charges +Q and -Q are fixed a distance r apart. The direction of the force on a test charge -q at A is… • Up • Down • Left • Right • Some other direction, or F =0

  5. Two charges +q and -q are on the y-axis, symmetric about the origin. Point A is an empty point in space on the x-axis. The direction of the E field at A is… Up Down Left Right Some other direction, or E = 0, or ambiguous y +q A x -q 2.3

  6. 2.1b How is the vector related to r1 and r2? r1 r2

  7. Coulomb's law: In the fig, q1 and q2 are 2 m apart. Which arrow can represent ? A q1 q2 B C D) More than one (or NONE) of the above E) You can't decide until you know if q1 and q2 are the same or opposite signed charges

  8. 2.2 What is ("from 1 to the point r") here? r1=(x1,y1) -q +q r=(x,y)

  9. Only click when you are DONE with page 1 (Part 1 i-iii) Is the answer to part 1- iii • A sum? • An integral over dy? • An integral over something else?

  10. Tutorial 1, part 2- Script r Only after you finish Part 2, what is in part 2-iv ? E) None of these!

  11. q q q q q 2.5 5 charges, q, are arranged in a regular pentagon, as shown. What is the E field at the center? • Zero • Non-zero • Really need trig and a calculator to decide

  12. q q q q 2.6 1 of the 5 charges has been removed, as shown. What’s the E field at the center? A) +(kq/a2) j B) -(kq/a2) j C) 0 D) Something entirely different! E) This is a nasty problem which I need more time to solve +y a +x

  13. To find the E- field at P=(x,y,z) from a thin line (uniform linear charge density ): What is ? A) X B) y' C) D) E) Something completely different!! 2.10 y dl' r' x r P=(x,0,0)

  14. 2.11 y dl' r'= (0,y',0) x r P=(x,0,0)

  15. ,so 2.11 y dl' r'= (0,y',0) x r P=(x,0,0)

  16. C A D E) NONE of the arrows shown correctly represents 2.12 To find the E- field at P from a thin ring (radius R, uniform linear charge density ): what is ? P=(0,0,z) y dl' x R B

  17. 2.13 To find the E- field at P from a thin ring (radius a, uniform linear charge density ): what is ? P=(0,0,z) dl' y a x A) B) a C) D) z E) Something completely different!!

  18. 2.16 Griffiths p. 63 finds E a distance z from a line segment with charge density : (0,0,z) x -L +L What is the approx. form for E, if z>>L? A) 0 B) 1 C) 1/z D) 1/z^2 E) None of these is remotely correct.

  19. 2.16 Griffiths p. 63 finds E a distance z from a line segment with charge density : (0,0,z) x -L +L What is the approx. form for E, if z<<L? A) 0 B) 1 C) 1/z D) 1/z^2 E) None of these is remotely correct.

  20. D) None of these To find E at P from a negatively charged sphere (radius R, uniform volume charge density ) usingwhat is (given the small volume element shown)? B C A 2.14 P=(x,y,z) (x’,y’,z’) z y x R

  21. (x,y,z) z y x R 2.15 P=(X,Y,Z) A) B) C) D) E) None of these dq

  22. (x,y,z) z y x R 2.15 P=(X,Y,Z) A) B) C) D) E) None of these

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