hi P.
Post #7 @crutschow explains the method.

Note the Vinput and Load current.
Increase the Vinput by say 0.1V, measure the Load current

Rin =ΔVin/ΔI load

Post the four values.

E

For Vin=7.2V ILoad = 2.98, For Vin=7.3V, ILoad=3

 

hi,
OK,
So now keep the Vin at say 7.2V and reduce the 4R load to 3.9R.
Measure change Vout and Iout
E

 

hi Peter,
Deleted my post #20.... I need my morning coffee.!

Use my post #22

E

 

Your circuit is not a resistor and there are no benefit to know that resistance. But if the task is task, in electronics there are only four methods how to calculate an any circuit. 1) equivalent circuits, where You step by step re-draw the circuit to less and less sophisticated version combining the serial or parallel connection laws; 2) Kirchoff laws equation system composing and solving what is damn attention demanding and solvable just by methods of linear algebra (matrix) or by MatLab but absolutely universal; 3) far less sophisticated but still very powerful method is extensive use of Norton theorem and last but no least is 4) Thevenin teorem. Even the bjt and/or fet may be calculated by means of some equations however that is rarely easy and accurate.

 

[/QUOTE]

hi,
OK,
So now keep the Vin at say 7.2V and reduce the 4R load to 3.9R.
Measure change Vout and Iout
E

For 4R Vout = 11.925 and Iout=2.97 and for 3.9R Vout=11.9105 and Iout=3.05

 

Your circuit is not a resistor and there are no benefit to know that resistance. But if the task is task, in electronics there are only four methods how to calculate an any circuit. 1) equivalent circuits, where You step by step re-draw the circuit to less and less sophisticated version combining the serial or parallel connection laws; 2) Kirchoff laws equation system composing and solving what is damn attention demanding and solvable just by methods of linear algebra (matrix) or by MatLab but absolutely universal; 3) far less sophisticated but still very powerful method is extensive use of Norton theorem and last but no least is 4) Thevenin teorem. Even the bjt and/or fet may be calculated by means of some equations however that is rarely easy and accurate.

Well, i understand that it is not very meaningful to calculate the resistance of this circuit but i want it cause i need to connect on its input a SEPIC converter that converts a voltage from a dc source to a specific level. So for the calculations of SEPIC converter components i need to know the resistance on its output.