I am an Electrical Engineer (graduated May ’72, Texas Tech U), but I never saw or even heard of a homopolar motor until last week, when I saw an electric motor made from four parts on National Geographic’s program, “None of the Above“. When I first saw it, I figured it must be a hoax. A DC motor had to have a commutator and two magnets.
Only when I was browsing around in Wikipedia did I find an article on the motor. I happened to have everything I needed, so I built one, not really expecting it to work. To my great surprise, it spun up to a few thousand RPMs in seconds. I read Wikipedia’s theory of operation, but it didn’t make sense. Today, I came across your wonderfully clear and simple explanation, and now I understand the motor perfectly.
I simply cannot thank you enough for your drawing and explanation.
Thanks for writing in— we’re glad to hear you enjoyed learning something new! The instructions for making the motor and the discussion of how it works are in our articles:
The Open Source Beehives project is currently running a crowdfunding campaign with the goal of gathering information from sensor equipped hives throughout the world to help solve bee population problems like colony collapse syndrome. The sensors can also be used by individual beekeepers to monitor the health of their hive.
Even without the sensors and the citizen science, their hive designs are beautiful.
While talking about egg sizes in the context of the Eggbot project, we realized that while we have access to a few samples, we do not have a good understanding of the normal variation in the sizes of various bird eggs.
The sizes of chicken eggs are well understood and well regulated, but for other types of bird eggs (like the emu egg above) the sizes are not necessarily so standard. If you have access to other types of eggs or eggshells, we’d like your help in gathering data about the size and variation in these other types of eggs.
We’ve set up a survey form to collect egg size data and we plan to post about our results once we have collected enough data.
To be clear, we’re interested in science beyond chemistry. We borrow this term to capture the spirit and magic of what the classic chemistry set spawned in the 1940s – 60s. We’re looking for ideas that can engage kids as young as 8 and inspire people who are 88. We’re looking for ideas that encourage kids to explore, create, build and question. We’re looking for ideas that honor kids’ curiosity about how things work.
We’ve delved into that spirit with our posts on Vintage Chemistry Manuals and Vintage Chemistry Sets. We also see it in our community in groups like Public Lab, with projects like Thermal Photography. It is exciting to see this contest trying to promote that spark of curiosity. Submissions are due in January, and we’re looking forward to seeing the winners when they’re announced in February. In the meantime, we would like to hear what you want to see in science kits for the future.
This week on the NPR radio show Science Friday, our co-founder, Windell Oskay, will be talking with Ira Flatow about Halloween hacks and projects and will likely be taking calls from listeners. Find out how to listen online and what radio stations will be broadcasting in your area. The show airs live from 2-4 p.m. Eastern Time (11 a.m. to 1 p.m. Pacific) and Windell should be on around 3:30 p.m. Eastern (12:30 p.m. Pacific).
Our archive of Halloween projects and hacks can be found here.