Solar Cell Physics Coursework (Calculating Internal Resistance)

[elyas22]

Basically I want to Calculate the internal resistance of a solar cell.

I set up a circuit with a voltmeter across the solar cell and an ammeter and variable resistor in series with the solar cell. The variable resistor is the load.

Image at http://elyaschaudhary.schools.officelive.com/video.aspx

As i change the resistance the value of current changes which is GOOD
However the Voltage stays the same BAD

This results is a graph with a horizontal Line implying that internal resistance is 0. BAD

I need the current and voltage to change i think to get a graph which will be able to give me the EMF and Internal resistance.

Could some one please explain how this is done

Thank you very much

Elyas

 

[Redbelly98]

How low in resistance did you go? If you short out the solar cell, you will definitely get a lower voltage.

 

[Delphi51]

If you replace the solar cell with a voltage source (V) and an internal resistance (r) in series, then calculate the measured voltage (V1), you will see that a constant V1 just means that the internal resistance r is small compared to R. You will need to do the experiment again with smaller values of R that do cause a change in V1 in order to calculate r.

 

[Redbelly98]

Also, the v-i curve for a solar cell is not a straight line.