Problem P. 4431. (March 2012)

P. 4431. One side of an old phonograph record was thoroughly wiped, thus this side was charged evenly to a charge of Q=1 C. The phonograph rotated the record of diameter d=300 mm, the number of revolution of the turntable was f=78/minutes. What is the magnetic induction at the centre of the record? Compare the orders of this magnetic induction and the magnetic induction of the Earth.

(5 pont)

Deadline expired on April 10, 2012.

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

Megoldás. Kb. \(\displaystyle 2\cdot10^{-12}\) T, ez többmilliószor kisebb, mint a földi mágneses mező tipikus erőssége.

Statistics:

40 students sent a solution.
5 points:	Antalicz Balázs, Barta Szilveszter Marcell, Bolgár Dániel, Csathó Botond, Czipó Bence, Dávid Bence, Filep Gábor, Fülep Andrea , Garami Anna, Janzer Olivér, Jenei Márk, Juhász Péter, Kollarics Sándor, Koncz Gabriella, Kovács 444 Áron, Laczkó Zoltán Balázs, Mázik László, Nagy Lajos, Papp Roland, Park Choong Eun, Seres Imre, Simig Dániel, Szabó 928 Attila, Szigeti Bertalan György, Ürge László.
4 points:	Agócs Fruzsina, Cseke Zsombor, Csóka József, Horicsányi Attila, Szilágyi 585 Dezső, Váncsa Szilárd.
3 points:	2 students.
2 points:	1 student.
1 point:	3 students.
0 point:	2 students.
Unfair, not evaluated:	1 solutions.

Problems in Physics of KöMaL, March 2012