You will find science fair projects on using lemons and other fruits and vegetables in www.terimore.com. You will also find over 300 other science fair projects on this site for all grade levels and virtually every subject. These projects are available immediately, on line,and include all materials needed, suggested procedures, what the judges are looking for, and how to do the research and make your presentation. Go to www.terimore.com.
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You should probably try google.com yea
You can try to google science projects, and look in those. There are some good sites in there. Hope this helps.
Creating a battery from a lemon is a very common project in many science text books. Here is a link where you can use the lemon "battery" to light a small flashlight's bulb. Hope it helps: