Characterizing Voltage Sources: Finding V0 and r using a Variable Resistor

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Homework Help Overview

The discussion revolves around characterizing a voltage source using a variable resistor connected to a battery. Participants are trying to determine the open circuit voltage (V0) and the internal resistance (r) based on data collected from a circuit graph as the resistance is varied.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the method for measuring V0, particularly questioning whether it should be taken at the point of smallest current. There is also inquiry into the significance of the y-axis intercept on the graph.

Discussion Status

Some participants have confirmed that their approach to measuring V0 was successful, while others are seeking to understand the underlying reasoning behind the method. There is an ongoing exploration of the relationship between V0, current, and internal resistance.

Contextual Notes

Participants are working with a graph that plots data from the circuit, and there are references to guidance provided by a teaching assistant regarding the measurement of V0. The discussion includes considerations of open circuit voltage and short circuit current in relation to internal resistance.

mitsuruangel
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Homework Statement


A variable resistor, R, is connected to the terminals of a battery (dashed box in the diagram). The graph below shows data collected in the circuit as R is varied. What is V0, in volts?

What is the internal resistance, r, in ohms?

should the V0 be measured at the top of the line where it is at the smallest current? because that is what the TA explained to do, I tried and I can't seem to get it right
 

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Did you extend the line backwards to where I=0(where it cuts the y axis)
 
mitsuruangel said:

Homework Statement


A variable resistor, R, is connected to the terminals of a battery (dashed box in the diagram). The graph below shows data collected in the circuit as R is varied. What is V0, in volts?

What is the internal resistance, r, in ohms?

should the V0 be measured at the top of the line where it is at the smallest current? because that is what the TA explained to do, I tried and I can't seem to get it right

And adding one more question to Dadface's post, what is special about where it cuts the y axis?
 
that worked! thanks
 
mitsuruangel said:
that worked! thanks

But why did it work. Do you understand that part?
 
Because V0 should be at lowest current (ie when it is 0) but the internal resistance keeps it from actually getting there?
 
mitsuruangel said:
Because V0 should be at lowest current (ie when it is 0)

That part is correct. V0 is the "open circuit voltage", so when no current is flowing. The other thing you can use to figure out the internal resistance is the "short circuit current". Once you have V0 and Rs, you have characterized your voltage source.
 

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