Problem in finding effective resistance

resistance

Look to this figure:
image

i have doubt in finding effective resistance b/w the terminals of this type of connections, during my school classes when I study to find effective resistances. When I study about wheatstone bridge. A method get me to find it, provided the relation $$frac{R_1}{R_3}=\frac{R_2}{R_4}$$ satisfied. Then there is no current through $R_L$ and circuit is simplified. But when the above relation does not satisfied, then how I find effective resistance? Is there any analytical method to find such solution or is this values only determine experimentally?

Best Answer

Think of R1,R3 as forming a Thevenin source, and R2,R4 a separate Thevenin source. Now Rl is merely connecting between two Thevenin sources, so the current thru it is easy to determine. With that you can compute the loaded voltage of the two Thevenin sources, which then pretty much tells you everything else.

That's just one way. There are various ways to eventually get all the voltages and currents in this circuit.