1. Announcements  Homework for tomorrow… Ch. 25, Prob. 65 & Ch. 26, CQ 2, Probs. 4 & 6 CQ12: 3 rd line to the right of -q 25.18: F A =(7.2 x 10 -4 N) jhat, F B =-(7.2 x 10 -4 N) jhat 25.40: F=(1.2 x 10 -5 N) jhat  Office hours… MW 12:30-1:30 pm TR 9-10 am F 1-2 pm  Tutorial Learning Center (TLC) hours: ??

2. Chapter 26 The Electric Field (E-Field Models & E-Field of Multiple Point Charges)

3.  The Electric Field is defined as…  The magnitude of the E-field of a pt. charge is… Last time… +

4. Permittivity constant..  Define a new constant..  so that…  Coulomb’s Law becomes…

5. Electric Fields & Superposition  Q: @ P, what is the E-field? P q1q1 q2q2 q3q3

6. Electric Fields & Superposition  Q: @ P, what is the E-field?  A: @ P, P q1q1 q2q2 q3q3

7. q3q3 q1q1 i.e. 26.1: The electric field of 3 equal pt. q’s Three equal positive point charges q are located on the y- axis at y = 0 and at y = ±d. What is the electric field at a point on the x-axis? q2q2 d d P x

8. i.e. 26.1: The electric field of 3 equal pt. q’s Three equal positive point charges q are located on the y- axis at y = 0 and at y = ±d. What is the electric field at a point on the x-axis? q2q2 q3q3 q1q1 d d P x

9. An Electric Dipole is…  2 equal but opposite charges separated by a small distance. Kinds:  Permanent Electric Dipole (i.e. H 2 O)  Induced Electric Dipole (i.e. polarized atom)  Dipole Moment… The Electric Field of a Dipole -q +q s

10. The Electric Field of a Dipole Calculate the electric field of a dipole on the axis of the dipole… -q +q s x y P

11. The Electric Field of a Dipole Calculate the electric field of a dipole on the axis of the dipole… Notice: r is distance measured from the center of dipole. -q +q s x y P

12. The diagram shows a positive charge +q and a negative charge –q with the same magnitude. The electric field at point P on the plane that bisects the dipole is: 1. Up. 2. Down. 3. Left. 4. Right. 5. Zero. Quiz Question 1 -q +q P

13. The Electric Field of a Dipole Calculate the electric field of a dipole in the plane that bisects the dipole. -q +q s x y

14. The Electric Field of a Dipole Calculate the electric field of a dipole in the plane that bisects the dipole. s x y -q +q

15. The Electric Field of a Dipole Calculate the electric field of a dipole in the plane that bisects the dipole. Notice: field is opposite to p & half the strength of on-axis field. -q +q s x y