Chapter 7 Dielectrics: Il Continuity Conditions at The interface Potential Energy Forces on conductors in the presence of Dielectrics Forces on dielectrics Displacement Current Frequency and Temperature dependence, Anisotropy
Chapter 7 Dielectrics: II ◼ Continuity Conditions at The Interface ◼ Potential Energy ◼ Forces on Conductors In The Presence Of Dielectrics ◼ Forces On Dielectrics ◼ Displacement Current ◼ Frequency and Temperature Dependence, Anisotropy
7. 1 Continuity Conditions at the Interface Between Two eala At the interface between the two media, the quantities V, E, and d must satisfy certain boundary conditions 1. The potent At the boundary btwn two media, v must be contin uous, otherwise av/ax would be oo, and E would be For a charge distribution in a finite region, the potential V is normally set to zero at infinity
2. The Normally Component of D (See Fig 7-1) Consider a short Gaussian cylinder drawn about a bound ary surface The cross-section area of the cylinder is s The boundary surface carries a free surface charge o f Then the flux of d emerging from the flat cylinder is equal to the charge enclosed (DnI-dn2)S=af Thus the bdry condition of D is (Dn1-Dn2)=af
S D D Figure 7-1 Gaussian cylinder on the interface between two media I and 2.The difference D-D, between the nomal components of D is equal to the surface density of free charge of
Examples If the boundary surface free charge of=0, then Dn1= Dn2 the normal component of d is continuous. this is usu ally the case for two dielectric media If the boundary is between a conductor and a dielectric, D=0 in the conductor, and Dn = of in the dielectric where o f is the free charge density on the surface of the conductor