Think about how a light bulb is powered… by electricity or a battery. But can a light bulb be powered by fruit? What a crazy concept!

Let’s explore the way a fall fruit can power a battery. Even though we may think that a pumpkin is a vegetable, by scientific definition it’s actually a fruit. You might have tried this experiment using a common, acidic fruit like a lemon or an orange; let’s try a pumpkin and see if it’ll work.

Gather Your Materials: What You’ll Need For Your Experiment

 Note:  With the exception of the pumpkins, all materials are available from a science supply store or Amazon. The good news is that they’re reusable for all sorts of electricity experiments when you’re done with this one.

• Knife (adult supervision required)
• 4- Pure zinc strip 
• 4- Pure copper strip
• 5 wires with alligator clips
• LED lightbulbs
• Multimeter
• 4-5 small, fresh pumpkins (if you’re careful, you can also decorate with these)

Understanding Circuits: The Basics of Electrical Flow

Before you begin, let’s remember some things about circuits.  First, the word circuit comes from the same root word as the word circle.  Keep that in mind. When you create a circuit; you need a complete circle.  If any end of your circuit is not connected, your lightbulb won’t light.

Circuits allow the continuous flow of electrons.  This is completed by linking a positive to a negative. 

The easiest way to visualize this is a battery that has a + (cathode) on one end and a – (anode) on the other.  If you line up batteries, positive ends connect to negative ends.  Reversing them will cause a disruption to the flow of power.

Formulating Your Hypothesis: How Many Pumpkins Will It Take?

Can one pumpkin power an LED light?  Can 2? 3? 4?  How many pumpkins will it take to turn on a lightbulb?  Will this work at all?

Step-by-Step Experiment: Building Your Pumpkin Power Chain

1.  Cut one slit into each side of each pumpkin.  Try to make each slit about the size of your zinc and copper strips.
2. Insert one zinc strip into one side of the first pumpkin.  Insert one copper strip into the other side, making sure they do not touch. Do the same with each pumpkin.

3. Chain two of your pumpkins together with an alligator clip by connecting a zinc strip to a copper strip.  Test your pumpkin with a voltmeter to see if you have power.  Record how much power you have in the table below.

4. Add a pumpkin by linking it to the second pumpkin with another alligator clip.  Test again.  Has the amount of power increased?  

Now comes the fun part- seeing if your lightbulb lights!

5. Try adding your lightbulb with another alligator clip to create a circuit.  Test to see that you have power with your multimeter.  Record the number below. Make sure you’re creating a pumpkin chain… linking the pumpkins by connecting a zinc strip on one to a copper strip on the next, and so on. Once you have connected your pumpkin, use and alligator wire with a clip to connect each end pumpkin to one side of your lightbulb.  Did it light?

6. Add your 4^th pumpkin in the same way as the third. Test and record the power. Now try the lightbulb.  Did it light?

If Your Lightbulb Doesn’t Light

If there is one part of your circuit that is broken or not hooked up properly, your lightbulb will not light.

Number of Pumpkins	Voltmeter Reading	Lightbulb Lights Up? (y or n)
1
2
3
4

Sketch your pumpkin chain, labeling each zinc plate with a “Z” and each copper plate with a “C.”

Conclusion

Was your hypothesis correct? 

The Chemistry of Pumpkins: Why They Conduct Electricity

The science behind it all:

The pumpkin contains acid, which starts the electrons moving, providing power.  Each pumpkin added increases the power of your circuit.  The zinc acts as a negative charge to your pumpkin battery and the copper acts as a positive charge.  The wires complete the circuit, providing enough power (hopefully!) to turn on your lightbulb!

Extend The Learning

Try this experiment with an even more acidic fruit, like a lemon or orange.  Does it make a difference?

Click below and download a lab worksheet that you can use to document your experiment.