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Yes,
Resistance is a passive measurement when measured using a 'dc' current source.
The current will be directly proportional to the applied voltage.
Over a range of applied voltages, the proportionality may not be linear, but at at each finite point of the V versus I plot,
Ohms Law must apply, otherwise you couldnt calculate the resistance.!
So the resistance is:R = V/I at every instant of V/I.
Ohm's Law is a methodology used to calculate something
*new*, not something we already know.
that's a great explanation of the differences between "ohmic" devices and nonlinear devices. if however, you did drop the voltmeter as in the above experiment, you wouldn't know what's in either black box. you only had one known data point for each box when the voltmeter got broken. you "peeked" into the box, because you already knew what was in the box. the whole idea of "black box" testing methods is that you create a set of data points and determine from your data what the box contains. one of my favorite "stumpers" for black boxes is the following:
a black box is connected to a 10V power supply with a 1 ohm output resistance with the following instruments attached, a voltmeter, an ammeter and a wattmeter. the voltmeter reads 5V, the ammeter reads 5A, and the wattmeter reads 0. what's in the box?
hi Al,
Reading your test results, I believe your conclusions are flawed.
For starters, any equation of 3 terms, where 2 terms are unknown, cannot be calculated to give a numerical value.
Consider the resistor in your example, measured using the known constant current and applied voltage. ie: 1Volt at 1mA = 1000R
You claim that when you apply a constant test current of 2mA, you 'know' that resistor is still 1000R, that is an assumption.!
The resistor could have changed value due to self heating as a result of the increase in current.
Therefore to be confident that the resistor hasnt changed value, you MUST measure the voltage across the resistor at the current of 2mA.
ohmic and non ohmic dosn't enter the equation.
a black box is connected to a 10V power supply with a 1 ohm output resistance with the following instruments attached, a voltmeter, an ammeter and a wattmeter. the voltmeter reads 5V, the ammeter reads 5A, and the wattmeter reads 0. what's in the box?