Problem 3.196

A circuit shown in Fig. 3.53 has resistances \(R_{1}=20 \Omega\) and \(R_{2}=30 \Omega\). At what value of the resistance \(R_{x}\) will the thermal power generated in it be practically independent of small variations of that resistance? The voltage between the points \(A\) and \(B\) is supposed to be constant in this case.