Investigate the maximum power output of a solar cell (photovoltaic cell).

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Fiona McDonnell                POWER OUTPUT OF A SOLAR CELL        01/05/2007


   I am planning to investigate the maximum power output of a solar cell (photovoltaic cell). As I will be using independent and dependent variables I will need to keep many conditions constant. The independent variables I could change are resistance of circuit, light intensity, colours of light and surface area of cell. My dependent variables I will need to keep constant are power, voltage and current.

   I have decided to change the light intensity because I think it is the biggest influential factor and it is also the one that can change the most. For example, when a solar cell is used to provide electricity to a home, it is attached on a roof. It is also the independent variable on which the whole solar cell operates. I will change the voltage of the light, and the distance away from the bulb of the solar cell.

   I will keep the resistance of the circuit the same by using a fixed resistor. The lamp used will always be the same lamp and no other light source will be available because I will blackout the rest of the area using black paper. The solar cell used will always be the same, as will the resistor and the ammeter. I will always repeat my experiment at least three times if possible to get an average of results. When I am measuring the distance of the lamp, I will use a fixed resistance of 12v and when I vary the volts I will have a fixed distance of 10cm away from the lamp. In these ways, my investigation will be a fair test.

   I will set up a simple circuit to find the power output and it will look like this:



Fixed Resistor

Solar Cell


Light Bulb

Power Supply

Retort Stand

   I will use a fixed resistor at 10Ω and an ammeter connected to the circuit to measure the current of the circuit. The light shone onto the solar cell will be from a filament lamp, connected in a separate circuit to a power supply, on which I can vary the voltage. The light is going to be

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connected to a retort stand so that I can vary the distance the light is from the solar cell.

   The voltage can be found out by using the formula, voltage = current x resistance, both of which I will know. I will then work out the power output of the solar cell by using the formula, power = voltage x current. In fact, I don’t actually need to work out the voltage, because if power = voltage x current and voltage = current x resistance I can use a new formula of power = resistance x current2.


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