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# Problem P. 4262. (May 2010)

P. 4262. An electron is shot at an initial speed of v0=4.107 m/s into a parallel plate condenser halfway between the plates. The distance between the plates and the length of the plates are unknown, and a constant voltage of U=500 V is applied between the plates. If a uniform magnetic field of induction B=6.25.10-5 Vs/m2 is also applied between the plates, in the appropriate direction, the electron goes through the plates without changing the direction of its motion, at a constant speed.

a) Determine the electric field between the plates of the parallel plate condenser.

b) Find the distance d between the plates.

c) If the magnetic field is ceased the speed of the electron increase by 6% when passes the condenser. What is the length of the plates L?

(4 pont)

Deadline expired on June 10, 2010.

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

Megoldás. $\displaystyle a)$ $\displaystyle E=v_0B=2,\!5 \cdot10^3$ V/m,

$\displaystyle b)$ $\displaystyle d=U/E=0,\!2$ m,

$\displaystyle c)$ $\displaystyle L\approx1,\!3$ m.

### Statistics:

 71 students sent a solution. 4 points: Balogh Gábor, Barta Szilveszter Marcell, Benyó Krisztián, Béres Bertold, Béres Orsolya Katalin, Bolgár Dániel, Burján Bence, Czigány Máté Gábor, Farkas Martin, Filep Gábor, Fonai Dániel, Hoksza Zsolt, Janosov Milán, Kaposvári István, Kovács 255 Márton, Kovács 444 Áron, Kovács Attila, Kungl Ákos Ferenc, Laczkó Zoltán Balázs, Lájer Márton, Lőrincz Dóra, Mayer Martin János, Miskó Gergely, Nagy 111 Miklós, Neumer Tamás, Pálovics Péter, Para Attila, Pázmán Koppány, Pető János, Pirka Benjámin Zoltán, Rácz Viktor, Szabó 928 Attila, Szabó Bence, Szatmári András Zoltán, Szöllősi Márton, Tamási Mátyás, Timkó Réka, Tóth Balázs, Tóth Csilla Ágnes, Varju 105 Tamás, Várnai Péter, Vuchetich Bálint, Zsámboki Richárd. 3 points: 23 students. 2 points: 3 students. 1 point: 2 students.

Problems in Physics of KöMaL, May 2010