1. Announcements  Homework for tomorrow… Ch. 26: CQ 4, Probs. 12 & 14 25.65: a) E 1 =(8.5 x 10 3 N/C) ihat-(4.0 x 10 3 N/C) jhat, E 2 =(1.0 x 10 4 N/C) ihat, E 3 =(8.5 x 10 3 N/C) ihat+(4.0 x 10 3 N/C) jhat b) Yes, as forces obey principle of superposition and F~E, E-fields must obey principle of superposition. c) E net =(2.7 x 10 4 N/C) ihat CQ2: a) 1 line to left of right chargeb) 3 lines to right of right charge 26.4: E = 7.6 x 10 3 N/C, 90 o below horizontal 26.6: a) 2 nCb) 180 N/C Office hours… MW 12:30-1:30 pm TR 9-10 am F 1-2 pm  Tutorial Learning Center (TLC) hours: MW 8-10 am, 12-6 pmR 8-12 pm, 2-6 pm T 8-1 pm, 2-6 pmF 8-10 am, 2-5 pm

2. Chapter 26 The Electric Field (The E-Fields of Rings, Disks, & Planes)

3.  Linear & surface charge densities  E-field of a rod of length L & charge Q in the bisecting plane..  E-field of an infinite line charge.. Last time… + + + + + + + + + + + + + + + + + + + L r P

4. Two protons, A and B, are in an E-field. Which proton has the larger acceleration? 1. Proton A 2. Proton B 3. Both protons have the same acceleration Quiz Question 1

5. A thin ring of radius R is uniformly charged with total charge Q. Find the E-field at a point on the axis of the ring. i.e. 26.4 E-field of a ring of charge..

6. A thin ring of radius R is uniformly charged with total charge Q. Find the E-field at a point on the axis of the ring. i.e. 26.4 E-field of a ring of charge..  Q: What about for –z?  Q: What about for –Q?

7. Positive charge, +Q, is uniformly distributed on the upper half of a semicircular rod and negative charge, –Q, is uniformly distributed on the lower half. What is the direction of the electric field at point P, the center of the semicircle? 1. Up. 2. Down. 3. Left. 4. Right. 5. Up and to the left. Quiz Question 2 P +Q -Q

8. A disk of radius R is uniformly charged with total charge Q. Find the E-field at a point on the axis of the disk. E-field of a disk of charge..

9. A disk of radius R is uniformly charged with total charge Q. Find the E-field at a point on the axis of the disk. E-field of a disk of charge.. Notice:  For z<0, same magnitude but opposite direction

10. A plane is uniformly charged with uniform surface charge density η. Find the E-field… E-field of a plane of charge.. ∞∞ ++++++++++++++++++++++++++++++++++++++

11. A plane is uniformly charged with uniform surface charge density η. Find the E-field… E-field of a plane of charge.. ∞∞ ++++++++++++++++++++++++++++++++++++++ Notice:  A constant!  Zero height dependence?