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B Solar Cell Current increases as Resistance increases Problem

  1. Dec 10, 2016 #1
    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, im a total noob when it comes to this stuff so anything is much appreaciated :)

    also, this is how im hooking up the resistors:
    http://www.mtmscientific.com/solar4.jpg
     
  2. jcsd
  3. Dec 10, 2016 #2

    Nugatory

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    Staff: Mentor

    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.
     
  4. Dec 10, 2016 #3
     
  5. Dec 10, 2016 #4
    Thank you so much! I just did what you said and it worked :) Now I can finally get some data!
     
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