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Turn Your Pencil Into a Dimmer Switch

If the holidays are in force in your house during the days of December, you might just have materials lying around that could shed a bit (or less) light on some fundamental principles involved in working with electricity and simple circuits. The Sliding Light: How to Make a Dimmer Switch Project Idea is a fun and hands-on electronics project that lets you explore what happens when you increase or decrease resistance in a circuit.

How does the electrical current output change relative to resistance? Shed some light on the situation to find out! (You'll need a No. 2 pencil. The eraser is optional!)


Making Connections

With homework on hold for the winter break, you might find it illuminating to shave down a spare No. 2 pencil (all the way to the graphite center!), hook it up to a tree light bulb and a 9 volt battery, and investigate the role of resistance in a circuit as you create a functional "dimmer," like ones you may have in your house that let you brighten or darken a room. Depending on where you touch the graphite core with the slider (to complete the circuit), you'll see a difference in the light output.

If you like to tinker, this is a fun project, and the results are ones you can see!

project photo

Taking It Further


If you don't already have a light meter, like like this one (available at Amazon.com), now might be a perfect time of year to let your parents know how useful such a tool might be for your exploration of electronics and electricity!

If the No. 2 pencil-based dimmer project inspires you, you might be interested in these other Science Buddies Project Ideas that use (or can be adapted to use) a light meter:


If you try this project out, just for fun, we'd love to know how it goes! Send us your story—or your images. We want to see!

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