Sorry, I couldn’t resist the ice tray pun. I just love simple and illuminating (yes, another pun) science experiments which don’t require any expensive equipment. And you can even recover most of the investment in this one after the students are done with the cash.
From Make Magazine: a Penny and Dime-powered LED.
The simple initial challenge of making a one cell battery with salt water, a dime and a penny can be easily extended to multiple cells in series to generate higher voltage. The LED allows experimentation with polarity. If you have a volt meter, students can measure voltages and design batteries for any number of applications from lighting an LED to powering a motor. They can measure the capacity of the battery, calculate the currents, and experiment with ways to improve the battery performance. (Bigger cells, polished electrodes, bigger multi-penny electrodes.) It’s a great open ended exploration: “Okay, now make your battery better!” or, “Okay, now can you make the same battery cheaper?”
Chemistry, Physics, Electrical Engineering and Electronics in one simple and inexpensive activity! Woohoo!