6.641,Electromagnetic Fields,Forces,and Motion Prof.Markus Zahn Lecture 7:Polarization and Conduction I.Experimental Observation A.Fixed Voltage-Switch Closed (v=V) Switch Eo As an insulating material enters a free-space capacitor at constant voltage more charge flows onto the electrodes;i.e.as x increases,i increases. B.Fixed Charge-Switch open(i=0) As an insulating material enters a free space capacitor at constant charge, the voltage decreases;i.e.as x increases,v decreases. II.Dipole Model of Polarization A.Polarization Vector P=Np =Nqd (p=gd dipole moment) N dipoles/Volume (P is dipole density) d+q \-q 6.641,Electromagnetic Fields,Forces,and Motion Lecture 7 Prof.Markus Zahn Page 1 of 276.641, Electromagnetic Fields, Forces, and Motion Lecture 7 Prof. Markus Zahn Page 1 of 27 6.641, Electromagnetic Fields, Forces, and Motion Prof. Markus Zahn Lecture 7: Polarization and Conduction I. Experimental Observation A. Fixed Voltage - Switch Closed (v=Vo ) As an insulating material enters a free-space capacitor at constant voltage more charge flows onto the electrodes; i.e. as x increases, i increases. B. Fixed Charge - Switch open (i=0) As an insulating material enters a free space capacitor at constant charge, the voltage decreases; i.e. as x increases, v decreases. II. Dipole Model of Polarization A. Polarization Vector P Np Nqd = = (p qd = dipole moment) N dipoles/Volume (P is dipole density) d q + −q