Mathematical and Physical Journal
for High Schools
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# Problem P. 4756. (September 2015)

P. 4756. A circular ring is made of a piece of metal wire of resistivity $\displaystyle \varrho$ and of width $\displaystyle 2a$. The radius of the central circle of the ring is $\displaystyle r$ ($\displaystyle r\gg a$). This ring is placed into uniform magnetic field of magnitude $\displaystyle \boldsymbol{B}_0$, which is perpendicular to the plane of the ring. Then the magnetic induction is decreased uniformly to zero in a time of $\displaystyle \Delta t$. Determine the magnitude of the induced magnetic field, $\displaystyle B_{\rm ind}$, at the centre of the ring.

(5 pont)

Deadline expired on October 12, 2015.

### Statistics:

 61 students sent a solution. 5 points: Asztalos Bogdán, Balogh Menyhért, Blum Balázs, Csenger Géza, Csire Roland, Csorba Benjámin, Csuha Boglárka, Csurgai-Horváth Bálint, Fehér 169 Szilveszter, Forrai Botond, Gémes Antal, Gergely 444 Kornél, Ghada Alshalan, Iván Balázs, Juhász 326 Dániel, Kardos Réka, Kovács Péter Tamás, Körmöczi Dávid, Körtefái Dóra, Mándoki László, Matusek Márton, Nagy 555 Botond, Németh Flóra Boróka, Páhoki Tamás, Pataki 245 Attila, Pázmán Előd, Radnai Bálint, Riskutia Balázs, Sal Kristóf, Szalai Istvan, Szántó Benedek, Szentivánszki Soma , Tófalusi Ádám, Tomcsányi Gergely, Tompa Tamás Lajos, Topa Lukács, Varga-Umbrich Eszter, Virág Barnabás, Zalavári Márton. 4 points: 15 students. 3 points: 2 students. 2 points: 2 students. 1 point: 3 students.

Problems in Physics of KöMaL, September 2015