dielectric conductor Teil 6 DIELEKTRIKA model assumptions polarization charges neutral charges move freely!! without current :!

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Ingrid Holtzer
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1 5 Teil 6 DELEKTRKA conductor charges move freely without current : fieldfree inside dielectric charges are fixed near atomic positions but they may be polarized: displacement by a fraction of the atomic size EX SS2014 C A A A H A E J A H K C A A A H A E J A H model assumptions polarization charges B H A E charges K C Dielectric = small polarizable spheres Residual charges appear at the surface Their field opposes the external field 8 ) neutral F B H A E 1 dielectric = J H charges K C 8 )

2 , ) * d b U polarization charges electric field at an interface Elektroden Dielektrikum B H A E U F 5 B H A E charges K C 1 dielectric = J H charges K C A L =? E v = E d, E A 8 =? A A L =? E A > = L =?, E E A L =? 8 =? = tan E? v = E? d Polarisierbarkeit Flächenladungsdichte : conductor : free charges atomares Dipolmoment : Polarisation : ~p = ~ E ~P = 0 ~ Ed ~ E v = frei dielektrische Suszeptibilität [ ~ D]=[ 0 ~ E]=[ ~ P ]=[ ]= apple C m 2 Feldstärke im leeren Kondensator 0 Feldstärke mit Dielektrikum ~ E d = frei pol 0 freie Ladungen Polarisations Ladungen dielectric : polarization charges Dielektrizitätskonstante des Vakuums ~D = 0 ~ Ed elektrische Verschiebung elektrische Flussdichte ~E d = E ~ v P/ 0 ~ = E ~ v Ed ~ ~E v =(1 ) E ~ d = E ~ d Dielektrizitätskonstante relative Permittivität Tensor

3 Elektrostatik in Natur und Technik Durchfluss Zytometrie Papierschnitzel ist vorher neutral. Kraftwirkung ist nur beobachtbar, wenn das Feld inhomogen ist. Nettokraft ist proportional zum Feldgradienten Piezo effect Piezo deformation crystal between two electrodes

4 Piezo elements Piezo elements 10 MHz 1500 m/s phased array Piezo elements 10 Milliarden in 2010

Elektrischer Durchbruch Feldemissionsmikroskop A E J A H R Q φ = f

D E H H @ A nominelle Vergrößerung: R/r 2 nm 1 mm Grenzen: Beugung

D F = K C R 5cm r 100 nm Das Feld ist invers proportional zum

Ruska 1932 He knew that electrons possess a wave aspect, so he

Ruska built the first crude electron microscope, capable of

Modern electron microscopes can magnify an object 2 million times,

5 Elektrischer Durchbruch Feldemissionsmikroskop A E J A H R Q φ = f c R = f q c r r. K H A A? D E H A nominelle Vergrößerung: R/r 2 nm 1 mm Grenzen: Beugung E σ ϵ 0 E r E R q/4πr2 Q/4πR 2 = R r 8 = K K F K F A / = 0? D F = K C R 5cm r 100 nm Das Feld ist invers proportional zum Kugelradius Elektrostatische Linsen Linsenpotentiale E. Ruska 1932 He knew that electrons possess a wave aspect, so he believed he could treat them in a fashion similar to light waves. Ruska built the first crude electron microscope, capable of magnifying objects 400 times. Modern electron microscopes can magnify an object 2 million times, they are still based upon Ruska's prototype. berechnete Trajektorien der geladenen Teilchen SEM image of the feeding basket of Antarctic krill: The purple ball is one micrometer in diameter.

FlüssigMetall onenquellen / = Rastertunnelmikroskop STM A J = 8

Elektronen tunneln durch Potentialbarrieren A A J H J = J E?

J B H H = A J = @ K C * A E? D J K C E? D J A A J H E?

D 2 D J A B B A J A H A K C J A = @ K C F = = H 2 = F E A H?

6 FlüssigMetall onenquellen / = Rastertunnelmikroskop STM A J = kev A A J = A A J = z mit 5 nm Auflösung schreiben Elektronen tunneln durch Potentialbarrieren A A J H J = J E? D A ) K B K C E B K A E A H J A K C = > Xerokopie, H = D J B H H = A J K C * A E? D J K C E? D J A A J H E? D A 0 = > A E J A H? D E? D J A J = K > J H = K H? D 2 D J A B B A J A H A K C J A K C F = = H 2 = F E A 6 A H J A E? D A EFeld der Erde 100 km A Blitzschläge pro Minute A

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