Mathematical and Physical Journal
for High Schools
Issued by the MATFUND Foundation
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Problem P. 4462. (September 2012)

P. 4462. A resistor of resistance R=8  is operated with the aid of the variable resistor of resistance R0=30  in the circuit shown in the figure. The e.m.f. of the voltage supply is U0=24 V, and its internal resistance is negligible.

a) Where is the pointer of the variable resistor when the voltage across the resistor is 12 V?

b) In this case, what percentage of the total dissipated power is the power dissipated in the resistor?

c) Between what values can the dissipated power in the resistor be varied? Between what values can the power given off by the voltage supply vary?

(4 pont)

Deadline expired on October 10, 2012.

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

Megoldásvázlat. a) A csúszóérintkező (alulról számított) 80 százalékos állásánál.

b) A fogyasztó teljesítménye 18 W, ez az összes felvett teljesítmény (48 W) 37,5 százaléka.

c) A fogyasztó teljesítménye 0 és 72 W, az áramforrás teljesítménye 19,2 W és 91,2 W között változhat.

Statistics:

 109 students sent a solution. 4 points: 52 students. 3 points: 23 students. 2 points: 20 students. 1 point: 6 students. 0 point: 6 students. Unfair, not evaluated: 2 solutions.

Problems in Physics of KöMaL, September 2012