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# Problem P. 4576. (November 2013)

P. 4576. The outer radius of a spherical shell, made of insulating material, is r2=0.2 m, and its inner radius is r1=0.15 m. The relative dielectric constant of its material is r=8.4. The shell is charged positively, and the charge is distributed evenly such that the charge density is =10-5 C/m3. Measured from the centre of the spherical shell where are those points at which the magnitude of the electric field strength is

aE1=3.103 V/m,

bE2=3.104 V/m?

(5 pont)

Deadline expired on December 10, 2013.

Sorry, the solution is available only in Hungarian. Google translation

Megoldásvázlat. $\displaystyle a)$ A gömb középpontjától 0,17 m és 0,76 m távol;

$\displaystyle b)$ 0,24 m távolságban.

(A változó dielektromos állandó miatt a gömbhéj külső felületénél az elektromos térerősségnek ,,ugrása'' van; a felületen ,,polarizációs töltéssűrűség'' alakul ki.)

### Statistics:

 35 students sent a solution. 5 points: Balogh Menyhért, Berta Dénes, Büki Máté, Csibi Levente, Di Giovanni Márk, Dinev Georgi, Fehér Zsombor, Forrai Botond, Janzer Barnabás, Kaposvári Péter, Olosz Balázs, Trócsányi Péter, Virágh Anna. 4 points: Blum Balázs. 3 points: 14 students. 2 points: 6 students. 0 point: 1 student.

Problems in Physics of KöMaL, November 2013