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To test what wavelength (or color) of light will work to produce the most current and voltage for a solar cell.


Different wavelengths of colored light will produce different amounts of current and voltage. Blue or green light will produce the greatest amount of current and voltage.


1. voltmeter (Protek A800 ™)
2. 2 solar panel kits (comes with solar panel, solar motor, ends etc)
3. 3 colored light filters (red, yellow, blue. Orange green and purple)
4. Technic LEGO Robotics Invention Kit ™
5. light source (sun)
6. Scotch ™ tape
7. Halogen lamp (Ikea ™)


Car Construction

A. 2 sides Lego car - 22cm long and 3 layers high.
B. top of car – 3 X 6.5cm by 4.5cm plank LEGO and 1 X 1cm by 6.5cm

C. Planks layed from the back end.

D. Count 5 holes from the 1cm by 6.5cm and put an 8 cm long pipe with a 1cm diameter (12 teeth) gear and a 3.5cm elastic pulley.

E. 1 layer down, 4 holes from the pipe another pipe 16 cm long. 4.5 cm (40 teeth) gear connected to the 1cm gear. 2 X 6cm d wheels on the out side driven by the gears.
F. Third layer, 3 holes from the end a 9.5 cm long pipe, 2 X 2.5 smaller running wheels centrally.

Solar panel construction

A. Two solar panels connected in series to the motor.

B. Motor and the solar panels to the car.

C. Elastic band attached from the motor to the 3.5 cm elastic gear.

D. No extra features were added to the car in order to maintain minimal weight. Total weight of car should be less than 220g.


1. Experiments performed at 10:30 AM and 1 PM on sunny days in April/05
2. Solar panels angled perpendicular to the sun.
3. Plastic colored filters taped to completely cover the solar panels.
4. Record current and voltage with voltmeter
5. Repeat step 3 with all the colors while recording the data.

Shockwave Videos of Solar Powered Car experiment
Test Car in Action (shockwave file)

Top view with Solar Cells

Car Design

Under side

Red Filter

Blue Filter

Yellow Filter

Primary Colour Filters

Purple Filter

Orange Filter

Green Filter

Secondary Color Filters


10:30 AM
1:00 PM
400 nmViolet
475 nm Blue
550 nm Green
600 nm Yellow
650 nm Red

The yellow colored light produced the greatest current at 49 ma (milliamps) 1 PM. The blue orange and red light gave the most amount of current using the halogen lamp at 29.5 ma. Throughout the experiment, the voltage stayed the same at 1.5 volts under all light conditions.

Results were similar with regard to the influence of light colour at 10:30 AM and 1 PM, but the current was consistently higher at 1 PM.

The halogen lamp produced similar results, but at a lower current.


Solar cells are composed of two thin layers of crystallized silicon. One layer is positively charged (P-type – created when the silicon is infused with Boron). The other layer is negatively charged (N-type – created when the silicon is infused with phosphorus or arsenic). The crystal structure of the silicon contains empty areas which allow for electron flow. When light penetrates the solar cell, electrons flow from the negatively charged layer to the positively charged layer. This flow of electrons creates a current.

Different wave lengths of light have different energy levels. Long wavelengths, (red) do not have enough energy to release an electron from a silicon atom. Short wave length (ultraviolet) light has so much energy that it goes straight through the solar cell, without releasing an electron. Light with wavelengths between 450nm-550nm have the appropriate amount of energy to release an electron from a silicon atom.

Time of day affects the current output of the solar panels, because the light intensity increases as the sun tracks directly overhead of the experiment. Current, which is the amount of electricity (electrons) that flows was measured in milliamps. Voltage is a measure of the force that electrons flow around the electrical circuit. The solar cells produce the same voltage with varying light intensity and wavelength.


My Hypothesis was that the blue and the green light will produce the most amount of current. That hypothesis should be rejected for the 10:30 and 1:00 test because the yellow light gave the greatest amount of current for both tests.
However, in the heat lamp test the blue light, along with the red and orange light, gave the most amount of current.

Because my results did not relate to my hypothesis, I wonder whether it depended on the angle at which I put the volt meter at, and at the angle the solar panel was angled.

If I were to redo this project, I would test the solar panels more than once and use different brands of solar cells.


1. Harness the power of the sun! Copyright 1998 Solar World
2. The new way things work, by David Macaulay and Neil Ardley, Editor David Burnie, Compilation copyright 1998
3. 100 Amazing Make-it-yourself Science Fair Projects, by Glen Vecchione, Sterling Publishing Co., Inc. 1994 New York


1. Clean energy Basics (NREL), July 6 2005.
2. Grade 7 projects, leader Composite School May 2004.
3. Science News For Kids, Riding Sunlight Science service 2005.
4. Online Science-athon Catching Sunshine TERC center for Partner-ships Interactive 2005