Mathematical and Physical Journal
for High Schools
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Problem P. 4550. (May 2013)

P. 4550. Two alike long, straight wires of diameter d, are at a distance of {D=50\,d}; their resistance is negligible and (L\ggD). One ends of the wires are connected through a battery of voltage U, and the other ends of the wires are connected through a resistor of resistance R. What is the value of R if the electric and magnetic forces exerted between the wires are equal?

(6 pont)

Deadline expired on June 10, 2013.


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

Megoldásvázlat.

\(\displaystyle R=\frac{1}{\pi} \sqrt{\frac{\mu_0}{\varepsilon_0}}\ln\frac{2D}{d}\approx 553\,\Omega.\)


Statistics:

17 students sent a solution.
6 points:Antalicz Balázs, Balogh Menyhért, Kollarics Sándor, Kovács 444 Áron, Olosz Balázs.
5 points:Sárvári Péter, Szabó 928 Attila, Váli Tamás.
4 points:1 student.
3 points:4 students.
2 points:1 student.
1 point:1 student.
0 point:2 students.

Problems in Physics of KöMaL, May 2013