Suppose \$R_{1}\$ and \$R_{2}\$ are replaced by resistors of unknown values which are different from those assumed in part (a).

Using a variable external voltage source, a student applies \$+1.5V\$ between terminals a and b (a is positive relative to b) and measures a current \$i_{0}\$ of \$-0.1A\$. When the external voltage is \$+3V\$, the external voltage source generates power and \$i_{0}\$ is \$+0.2A\$.

Recalculate the Thevenin voltage and resistance in this case, assuming all sources are ideal.

I am not sure how to approach this.

## Best Answer

Think of a black box that you are told is a Thevenin source. You take two different pairs of current,voltage measurments. How would you solve that?

Do you need to know if the inside is made of several sources with a mesh of resistors, or single voltage source with series resistance? How would you tell the difference between these two cases?

Hint: much of the details of this problem are a distraction to see if you fall for getting lost in the minutia instead of thinking about the whole problem.