Rheostat, a device used to regulate an electric current by increasing or decreasing the resistance of the circuit. Some common uses of the rheostat are to dim lights, to control the speed of an electric motor, and to control the volume of a radio. The accompanying diagram shows a simple rheostat. Current flows into the resistance coil and from the resistance coil through the slider. When the control knob is turned, the slider moves along the coil; the amount of resistance is thus changed by varying the length of the current's path through the resistance coil.
It was a grand day for humankind when the first Faraday cage came to life; these cages have given rise to all sorts of technological innovations. How much do you know about these wiry wonders?
Unlike the cheap microscopes you peered into in school, these advanced instruments can breathe rich detail into the tiny world around us, including the world of nanotechnology.