A new technique can measure the velocity of electrons in an electric current inside a crystal. A related technique mapped the density of electrons in the crystal using MRI. Image Credit: Phys. Rev. Lett. 96, 037601 (2006)
Like traffic cops with radar guns, physicists can now gauge the speed of electrons in a current. Researchers have recently described a speed-measuring system that uses magnetic resonance and demonstrate a test in which they verified Ohm's Law by directly observing electrons. The technique could eventually create the first images of the flow of electrons through materials at the micron scale.