Have you ever needed a low-value resistor for a low-voltage battery-powered circuit? Say, something in the range of 10-100 ohms? Finding this value of resistor can be difficult, if not impossible. In cases like this, you might be better off making your own resistor.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.