Bài giảng "Vật liệu học - Chương 6: Electrical properties" cung cấp cho người học các kiến thức về Ohm’s law, energy levels of an isolated atom, conduction & electron transport, charge carriers in insulators and semiconductors, energy bands, the mass action law,. . | Bài giảng Vật liệu học - Chương 6: Electrical properties Chapter 6 Electrical properties Ohm’s law 1 • Ohm's Law: V=IR voltage drop (volts = J/C) resistance (Ohms) C = Coulomb current (amps = C/s) • Resistivity, : -- a material property that is independent of sample size and geometry surface area RA of current flow l current flow path length • Conductivity, 1 2 Which will have the greater resistance? 2 2 8 D R1 D 2 D 2 2 R1 2D R2 2D D 2 2 8 2 Analogous to flow of water in a pipe Resistance depends on sample geometry and size. 3 Further definitions J= E 5 6 7 CONDUCTIVITY: COMPARISON • Room temperature values (Ohm-m)-1 = ( m)-1= S m-1 METALS conductors CERAMICS -10 Silver x 10 7 Soda-lime glass 10 -10-11 Copper x 10 7 Concrete 10 -9 Iron x 10 7 Aluminum oxide 9 EXAMPLE: What is the minimum diameter (D) of the wire so that V < V? ( = x 107 (Ohm-m)-1) 100 m Cu wire - I = A + V 100 m < V V R A D 2 A I 4 x 107 (Ohm-m)-1 Solve to get D > mm 10 Energy levels of an isolated atom 11 12 13 ELECTRON ENERGY BAND STRUCTURES 14 BAND STRUCTURE .
