Section 6A Electrical

Section 6A Electrical - Section 6 Electrical Properties...

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MATE 210 Section 6 Electrical Properties (Smith Chapter 14 - skip 14.8) The electrical properties of a material dictate if it’s a conductor, insulator or semiconductor?
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MATE 210 Material Elect Resistivity, Ω− m Steel alloy 1020 1.60 x 10 -7 Stainless alloy 304 7.2 x 10 -7 Aluminum alloy 1100 2.9 x 10 -8 Copper C110000 1.72 x 10 -8 Si (intrinsic) 2.5 x 10 3 GaAs (intrinsic) 10 6 Glass (soda-lime) 10 10 -10 11 Polyethylene 10 15 Polystyrene >10 14 Wood (Douglas fir) 10 14 -10 16 Solid materials exhibit huge range of electrical conductivity: • over 27 orders of magnitude! • classify materials based on σ: conductor insulator semiconductor conductivity ( σ ) : ease in which material is capable of conducting at flow of electrons metals ceramics polymers ρ σ 1 = V = IR (ohms law) V volts (J/C) I amperes (C/s) R ohms (V/A) P watt (J/s) = VI l RA = Resistivity of material ( ρ ) A = cross-sectional area (m 2 ) current l = distance (m) for voltage drop
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MATE 210 In an atom: each electron has it’s own energy level (electron configuration ) In a crystal lattice, many atoms: electron energy levels interact form energy bands Energy Bands in Solids Si (14) 1s 2 2s 2 2p 6 3s 2 3p 2 Pauli exclusion principle
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MATE 210 Electronic Band Structure Energy VB CB (b) Metal: overlap (c) Insulator: large gap (d) Semiconductor: small gap conductivity outermost electrons in the valence band (VB) empty conduction band (CB)
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MATE 210 Semiconductor Materials
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MATE 210 Conduction in Metals Metals: • vacant energy sites always nearby • little energy needed to be excited and free many free electrons high conductivity VB CB
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Section 6A Electrical - Section 6 Electrical Properties...

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