Suppose two resistors of impedance r1 and r2 are placed in series and held at different physical temperatures, t1 and t2. We would like to model this series combination of noisy resistors as a single noiseless resistor with an impedance of r = r1 + r2, together with a noise source with an effective temperature of te. In short, we want the two models shown in the accompanying figure to be equivalent. Assuming the noise produced by the two resistors is independent, what should te, the effective noise temperature of the series combination of resistors, be? If the two resistors are held at the same physical temperature, is the effective temperature equal to the true common temperature of the resistors for a parallel combination of resistors.

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r1 (noiseless) rms. 1 1' 1 γ1 + 7.2 (noiseless) 2 (noiseless) ims 4krAf rnms. 2