Mathematical and Physical Journal
for High Schools
Issued by the MATFUND Foundation
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# Problem P. 4724. (March 2015)

P. 4724. The working temperature of the tungsten filament of an incandescent lamp rated at 230 V and 100 W is $\displaystyle 2400~{}^\circ$C. In an experiment the voltage applied to the lamp is gradually increased from zero, and it can be seen that the filament begins to glow at 17 V. What is the temperature and the resistance of the filament in this state, and how much power is dissipated in this state of the bulb?

We can assume that the emitted power is proportional to the fourth power of the temperature measured in Kelvins, the fifth power of the resistance is proportional to the sixth power of the absolute temperature and heat conduction is negligible.

(5 pont)

Deadline expired on April 10, 2015.

### Statistics:

 39 students sent a solution. 5 points: Asztalos Bogdán, Balogh Menyhért, Bartók Imre, Berta Dénes, Blum Balázs, Bugár 123 Dávid, Büki Máté, Csathó Botond, Csire Roland, Csurgai-Horváth Bálint, Fehér Balázs, Fekete Balázs Attila, Fekete Panna, Forrai Botond, Fülöp Erik, Gróf Tamás, Holczer András, Iván Balázs, Jakus Balázs István, Kaposvári Péter, Kasza Bence, Kovács Péter Tamás, Lőrincz Zoltán, Marosvári Kristóf, Németh Flóra Boróka, Olosz Balázs, Öreg Botond, Páhoki Tamás, Pázmán Előd, Rózsa Tibor, Sal Kristóf, Szántó Benedek, Tófalusi Ádám, Trócsányi Péter. 4 points: Boldizsár Bálint, Horváth Botond István, Németh 017 András, Szentivánszki Soma . 1 point: 1 student.

Problems in Physics of KöMaL, March 2015