Mathematical and Physical Journal
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Problem P. 4453. (May 2012)

P. 4453. The density of the energy of the electric field inside a straight cylinder shaped metal rod is constant, its magnitude is w_{\text{el.}}= 2\cdot 10^{-17} J/m3; the density of the energy of the magnetic field inside the rod at a distance of r=2 cm from the symmetry axis of the rod is w_{\text{magn.}}= 0.4 J/m3.

a) What is the resistivity of the material of the rod?

b) What kind of metal was the rod made of?

(5 pont)

Deadline expired on June 11, 2012.


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

Megoldásvázlat. a) \varrho=\frac{r}{2} \sqrt{\frac{\mu_{0}}{\varepsilon_{0}}\,\frac{w_{\rm el.}}{w_{\rm magn.}}}\approx 2{,}6\cdot 10^{-8}\,\Omega\,\rm m.

b) Alumíniumból.


Statistics:

32 students sent a solution.
5 points:Agócs Fruzsina, Antalicz Balázs, Barta Szilveszter Marcell, Bingler Arnold, Bolgár Dániel, Büki Máté, Csathó Botond, Czipó Bence, Filep Gábor, Garami Anna, Horicsányi Attila, Janzer Barnabás, Janzer Olivér, Juhász Péter, Kacz Dániel, Kollarics Sándor, Laczkó Zoltán Balázs, Nagy Lajos, Papp Roland, Seress Dániel, Simig Dániel, Szabó 928 Attila, Szigeti Bertalan György, Ürge László.
4 points:Csóka József, Fülep Andrea , Koncz Gabriella, Medek Ákos, Olosz Balázs.
2 points:3 students.

Problems in Physics of KöMaL, May 2012