Solving the Black Box Circuit: Determining Impedance & Resistance

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To determine the impedance and resistance of a black box with two wires, one can measure the open-circuit voltage and short-circuit current. Although the exact internal configuration may remain unknown, these measurements allow predictions of circuit behavior under various loads. The term "passive" indicates the absence of active components like transistors, but power sources can still be present. For instance, if a battery is in series with a resistor, tests can reveal the voltage and current characteristics, aiding in understanding the circuit's response. Ultimately, knowing the equivalent circuit is sufficient for predicting outcomes with different load resistors.
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if a black box was given,with two wire pull out from the box.no other additional info was given,then how will you determine the impedance in the circuit?what is the resistance?if given that is a passive circuit,what will the circuit look like?
seem the task quite challenging.
 
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What would happen if you connected it in series/parallel with a know resistor?
 
the impedance will rise/fall?i am newbie in electronic,not too sure what you want to hint.
 
"Passive" doesn't mean it can't contain power sources. Just no transistors, opamps or other ICs.

You would measure the voltage out without a load and the current out into a short circuit.

You may not be able to work out exactly what is in the box, but you would be able to predict how it would behave under different load conditions.

Imagine a circuit where you had a battery in series with a resistor inside your box.
If you did the above tests, what would you be able to work out about the battery and the resistor?
Remember that if there is no current flowing in a resistor, there is no voltage across it.
 
could we probably know the circuit configuration in the box by guessing?given the circuit inside is passive circuit.
 
Unless the circuit happened to be a battery in series with a resistor, you could not guess what it really was.

But it doesn't matter. If you know what it is equivalent to, you can predict what would happen with different load resistors. That is all you need to know.

For example, if you had two equal resistors in series across a battery, and took the output from across one of them, the open circuit voltage would be half the battery voltage, but you couldn't tell there was a higher voltage battery present without taking the screws out of the box.
 
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