How to Make a Grapefruit Power a Light Bulb

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Things You'll Need

  • 1 medium-sized grapefruit

  • 1 copper nail or screw (about 2 inches long)

  • 1 zinc nail or screw (about 2 inches long)

  • 1 holiday light bulb with 2-inch leads, aka wires (make sure there is enough wire to connect the two nails)

  • Electrical tape

Make a Grapefruit Power a Light Bulb

Batteries come in many different shapes and sizes: alkaline, zinc chloride, lithium ion, and yes, even grapefruits. The acidity in citrus fruits (such as lemons, limes and grapefruits) allow their juices to conduct electricity. In this fun and easy experiment (ages 10 and up), you can create a grapefruit battery powerful enough to light up a small Christmas light. This experiment shows how citrus fruits, like a grapefruit, can generate small electric currents.


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Step 1

Prepare the grapefruit. Gently roll the grapefruit on a hard surface, like a table or counter top, to get the juicies flowing inside of it. You can also squeeze the fruit with your fingers. Be careful not to break the skin of the grapefruit! Use another grapefruit if you accidentally puncture your first one.


Step 2

Push the copper nail into the grapefruit. The tip of the nail (the sharp end) should be at the center of the fruit. Make sure the nail doesn't poke through to the other side of the grapefruit.

Step 3

Place the zinc nail into the grapefruit. The zinc nail should be located 2 inches from the copper nail. Again, the tip of the nail should be near the center of the fruit, but don't let the zinc nail touch the copper nail.


Step 4

Take off the insulation covering the leads (wires) of the light bulb. Remove about 1 inch of the insulation to uncover the wires underneath. Make sure you expose enough wire to wrap around both nails.

Step 5

Take one wire and wrap it around the zinc nail. Use some tape if the wire keeps slipping off.


Step 6

Take the other wire and wrap it around the copper nail.

Step 7

Once both wires are attached to the nails, the light bulb will turn on!


Use an LED light bulb for the experiment. LED bulbs work best since they need the least amount of energy to turn on.

Substitute the grapefruit with other fruit and vegetables (lemons, limes, potatoes) to see which one powers the light bulb the best.