Question

Find the internal resistance

This was a part of the analysis for a lab which confuses me.

We have the following system:
* Two power supplies connected opposite one another so that the positive (+) side of one supply goes into the positive (+) side of another supply.

* A single 100 ohm resistor connected in series with the two power supplies.

Both power supplies have an internal resistance that will change with varying voltage.

How can I use the voltage before turning on the circuit, after turning on the circuit, and the current provided to find internal resistance?

Answer 1

Two power supplies connected opposite one another so that the positive (+) side of one supply goes into the positive (+) side of another supply
Both power supplies will try to push current against each other. Supposedly one be V1 and the other V2, then resultant voltage supplied by them is V1-V2
Do you get this part?

Answer 2

Yeah, I get that

Answer 3

Now if the circuit is not on, there is no current flow and we can't find anything from that

Answer 4

Let R1 and R2 be the internal resistances of the power supplies V1 and V2. If the power supplies are identical then our analysis will be easy. Do you understand this?