Solar Cell Current increases as Resistance increases Problem

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Discussion Overview

The discussion revolves around the unexpected behavior of current measurements in a solar cell experiment, specifically how current increases with resistance, contrary to typical expectations. Participants explore the setup and measurements related to IV curves, focusing on the correct use of multimeters in measuring current and voltage.

Discussion Character

  • Technical explanation, Conceptual clarification, Homework-related

Main Points Raised

  • One participant describes their experience measuring current and voltage in a solar cell setup, noting that current increases with resistance, which is counterintuitive.
  • Another participant explains that the multimeter should be connected in series for current measurements, suggesting that the observed behavior may be due to incorrect connections.
  • A similar point is reiterated by a different participant, emphasizing the importance of series connections for accurate current readings and clarifying that voltage measurements can be taken in parallel without issue.
  • The original poster reports success after following the advice given, indicating that the issue was resolved by correcting the multimeter connection.

Areas of Agreement / Disagreement

Participants generally agree on the correct method for connecting the multimeter for current measurements. The initial confusion regarding the behavior of current with resistance is resolved through clarification, but the original misunderstanding remains a point of discussion.

Contextual Notes

The discussion does not address any potential limitations of the experiment or assumptions about the solar cell characteristics. There is no exploration of the underlying physics that would explain the initial observations.

Who May Find This Useful

Individuals interested in solar cell experiments, multimeter usage, or those new to electrical measurements may find this discussion beneficial.

PVJ2016
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Hi everyone, so I'm trying to achieve IV curves based on how this website had done below:
http://www.voltaicsystems.com/blog/solar-charger-tutorial-part-2/

But whenever I increase the resistance, the amperage increases rather than decreases! For example, when I use a 500 ohm resistor the amperage is 500 uA but when I use a 3.6 ohm resistor the amperage is 30 uA. The voltage seems to increase when more resistance is applied so nothing wrong there... could this be a problem with my multimeter? I tried this with two different solar cells and both have the same issue. BTW, I am a total noob when it comes to this stuff so anything is much appreaciated :)

also, this is how I am hooking up the resistors:
http://www.mtmscientific.com/solar4.jpg
 
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For amperage measurements you want the multimeter connected in series, not in parallel. What's happening here is that some of the current is flowing through the resistor and some of it is flowing through the multimeter, and the multimeter is reporting only the fraction that is flowing through it. Google for "ammeter parallel" for more on this.

For the voltage measurement, the parallel connection is fine; you're comparing the voltage at two points so you just need a probe at each point. No noticeable current flows through a multimeter doing a voltage measurement.
 
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Nugatory said:
For amperage measurements you want the multimeter connected in series, not in parallel. What's happening here is that some of the current is flowing through the resistor and some of it is flowing through the multimeter, and the multimeter is reporting only the fraction that is flowing through it. Google for "ammeter parallel" for more on this.

For the voltage measurement, the parallel connection is fine; you're comparing the voltage at two points so you just need a probe at each point. No noticeable current flows through a multimeter doing a voltage measurement.
 
Thank you so much! I just did what you said and it worked :) Now I can finally get some data!
 
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