Millikan's experiment

Testo e immagine adattati da

Halliday - Resnick - Crane

Fisica II

Dipolo

Un dipolo elettrico è un sistema composto da due cariche elettriche uguali e opposte di segno. È uno dei più semplici sistemi di cariche che si possano studiare e rappresenta inoltre l'approssimazione basilare del campo generato da un insieme di cariche globalmente neutro tramite lo sviluppo in multipoli di quest'ultimo.

Immagini adattate dal libro

Halliday, Resnick, Krane, Fisica 2

n.14 - Esercizio - elettrostatica

Volcanoes under Antarctic waters

"Scientists from British Antarctic Survey (BAS) have discovered previously unknown volcanoes in the ocean waters around the remote South Sandwich Islands. Using ship-borne sea-floor mapping technology during research cruises onboard the RRS James Clark Ross, the scientists found 12 volcanoes beneath the sea surface — some up to 3km high. They found 5km diameter craters left by collapsing volcanoes and 7 active volcanoes visible above the sea as a chain of islands."
More http://www.antarctica.ac.uk/press/press_releases/press_release.php?id=1541

An acoustic superlens from a few cans of cola

""Acoustic metamaterial" may sound exotic, but researchers in France have managed to assemble one from a few multipacks of cola cans. Arranged in a grid, the drinks cans act as a superlens for sound, focusing acoustic waves into much smaller regions than their metre-long wavelengths typically allow. The cans act as resonators, directing the volume of the sound to peak in a space just a few centimetres wide, and this heightened precision could improve acoustic-actuator systems."

How to make a superlens from a few cans of cola - physicsworld.com

n.13 - due piani carichi

Two infinite sheets of  electric charges with uniform densities intersect at right angles. The plane of the figure is perpendicular to the planes. Let us suppose that changes cannot move.
a) Find the magnitude and direction  of the electric field everywhere and sketch the lines of the field, in the case that a sheet has positive density (+sigma) and the other an equal but negative density (-sigma).
b) find the magnitude and direction of the electric  field everywhere and sketch the lines of the field, in the case that the two sheets have the same densitity with the same positive sign, + sigma.
c) Find the difference of potential V(A)-V(B), between the point A and B placed at a distance d on a line in the plane of the figure at 45° with respect to the charged planes.

n.12 - una piccola sfera

n.11 - tre piani

n.10 - due piani

n.9 - tre cariche puntiformi