Mathematical and Physical Journal
for High Schools
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Problem P. 4253. (April 2010)

P. 4253. How many electrons should be removed from a metal sphere of radius 1 cm, so that its electrostatic energy equals the energy loss due to mass defect? What would the electric potential of the sphere be in this case?

(4 pont)

Deadline expired on May 10, 2010.


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

Megoldás. \(\displaystyle N=\frac{2m_{\rm e}c^2r}{ke^2}\approx 7\cdot10^{12}\), a potenciál pedig \(\displaystyle U=\frac{2m_{\rm e}c^2}{e}\approx 1000~\)kV.


Statistics:

29 students sent a solution.
4 points:Béres Bertold, Farkas Martin, Filep Gábor, Galgóczi Gábor, Janosov Milán, Kaposvári István, Kovács 444 Áron, Kungl Ákos Ferenc, Laczkó Zoltán Balázs, Lájer Márton, Pálovics Péter, Para Attila, Pázmán Koppány, Szabó 928 Attila, Varju 105 Tamás, Várnai Péter, Zsámboki Richárd.
3 points:Balogh Gábor, Hartstein Máté.
2 points:5 students.
1 point:3 students.
0 point:2 students.

Problems in Physics of KöMaL, April 2010