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**Announcements**• Homework for tomorrow… (Ch. 25 Prob. 62, Ch. 26 Probs. 3 & 5 ) CQ13: a) 4F b) 4F 25.12: a) 0.90 N b) 0.90 m/s2 25.35: 4.3 x 10-3 N, 252° CCW • Office hours… MW 12:30-1:30 pm TR 9-10 am F 10-11 am • Tutorial Learning Center (TLC) hours: M 8-1 pm, 3-6 pm, W 8-1 pm, 2-6 pm TR 8-6 pm, F 8-2 pm**Chapter 26**The Electric Field (E-Field Models & E-Field of Multiple Point Charges)**Last time…**• The Electric Field is defined as… • The Electric Field of a point charge is… +**Permittivity constant..**• Define a new constant.. • so that… • Coulomb’s Law becomes…**Electric Fields & Superposition**• Q: @ P, what is the electric field? P q1 q2 q3**Electric Fields & Superposition**• Q: @ P, what is the electric field? • A: @ P, P q1 q2 q3**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? q1 d P q2 x d q3**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? q1 d P q2 x d q3**The Electric Field of a Dipole**An Electric Dipole is… • 2 equal but opposite charges separated by a small distance. Kinds: • Permanent Electric Dipole (i.e. H2O) • Induced Electric Dipole (i.e. polarized atom) • Dipole Moment… +q s -q**The Electric Field of a Dipole**Calculate the electric field of a dipole on the axis of the dipole… y +q s x -q**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. y +q s x -q**Quiz Question 1**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: • Up. • Down. • Left. • Right. • Zero. +q P -q**The Electric Field of a Dipole**Calculate the electric field of a dipole in the plane that bisects the dipole. y +q s x -q**The Electric Field of a Dipole**Calculate the electric field of a dipole in the plane that bisects the dipole. y +q s x -q**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. y +q s x -q