how do i find the internal resitance of a solar cell. help me plz?

Question

i have not been given anything or told anythign for that sake...i need 2 find teh internal resistance of a solar cell and vary the light intensity if i have time... i dont understand how to go about it..what to use..the digital meter???? e.t.c plz help me as soon as possible..thank you very much...n oh yh plz explain it in laymen terms :D thank you so much

Answer 1

Well internal resistance of a solar cell is calculated by measuring the voltage developed across and the current passing through it in a closed circuit. So basically what you do is connect a voltmeter (digital one works) across the cell +ve and -ve pin. Across the same terminals connect a variable resistor and ammeter combination(which are connected in series). So basically you will have Cell in parallel with Voltmeter in parallel with a combination(resitor in series with ammeter). now we need the max and min current through the cell, so what you do is increase the variable resistance to max to get the minimum current, decrease the variable resistance to zero to get the maximum current. At these points measure the current in the ammeter reading. now to get the middle points or current, step by step decrease/incresase the variable resistance and measure the corresponding ammeter reading. That way you will note all the current readings and the voltage readings. Now all you need to get V/I to get the resistance values. You can get these values for different intensities of lights.

Answer 2

For a given light intensity, measure the voltage across the cell with no load, and again with the load. If the internal resistance were zero, the voltages would be equal. You can model the cell as a voltage source whose value is the no-load voltage, and a series resistor. The point of doing it at various light intensities is that the equivalent internal resistance might not be the same at all values of light intensity.