# What affects the voltage output of a solar panel?

Thaddeus Cheung (4534)        Physics Coursework – Solar Cell

Planning

## Aim

The aim of the investigation is to find out how the distance between a light point source and a photovoltaic cell affects the output potential difference.

## Hypothesis

I predict that the further the distance, the smaller the output potential distance

Inverse square law for light intensity

(Taken from the website - http://hyperphysics.phy-astr.gsu.edu/hbase/vision/isql.html#c1)

“Inverse square law for light intensity against distance: As the distance between an observer and a light source increases, the observable brightness decreases with d-2.  Light spreads out over an increasing area of space to decrease apparent brightness. (Figure 1.1)

Figure 1.1 (http://www.astrosociety.org/education/publications/tnl/32/images/fig5.gif)

Because, Pin is proportional to area-1 and area is proportional to distance2, therefore Pin is proportional to distance-2 (figure 1.2). This supports my prediction that the output potential difference will be much smaller when the distance between the point source and the PV cell increases. Of course, my hypothesis assumes 100% efficiency and no influence from background light and other factors that may affect the experiment in anyway.

1.2 Prediction of outcome (Pin α distance-2)

## Apparatus list

The list of apparatus to be used is:

A ray box is chosen over a light bulb as the light bulb will emit light out of all directions, while the ray box’s light can be controlled to be emitted out through one direction, to the solar cell.

## Method

1. Gather all the equipment
2. Measure the radius of the light bulb using vernier callipers and add it to the distance between the light bulb and the end of the ray box.
3. Plug in the power pack and connect it to the ray box
4. Tape the black paper on the table, with an inch going underneath the ray box
5. Use the length measured from step 2 to find 10cm away from the point source and mark it on the black paper.
6. Mark 5cm increments from the base(10cm) mark until you get to 60cm
7. Attach the solar cell to the clamp and clamp it on the table with the first marker. Use a set square to make sure that the solar cell is 90° to the table.
8. Turn on the voltmeter and note down the volt output without the ray box on. This is the background reading
9. Switch on the power pack and take the reading from the voltmeter. Subtract the background reading from this current reading
10. Turn off the power pack and repeat steps 8 and 9 two more times to get an average
11. Do steps 7-10 increasing the distance by 5cm (next marking) until the solar cell is 60cm away from the point source

## Fair testing

There are possible variables which will be kept constant in the experiment as they might affect the readings if not kept constant.

The solar cell will always be 90° to the table as the angle affects how much light is taken in. If the angle is not constant then the readings will be irregular as the light intensity will vary. Each time the solar cell is moved, a set square will be used to check that it is still 90° to the table.

The voltage used will be the same. If the voltage ...