National Geographic : 1951 Dec
© National Geographic Society 4' Invisible Electrons Are "Weighed" to Measure Units of Electricity To measure the faraday, a basic unit of electrical quantity, a scientist prepares to determine the mass, or weight, of atomic particles by whirling them on a spiral path in the omegatron. Standards for the volt, ampere, ohm, and watt are also set by the Bureau. Ektachromes by Willard IR. Culver + Plastic Headgear Tests the Efficiency of Earphones With this device the Bureau determines how well earphones work on ears. Sound from the earphone is picked up inside the ear cavity by a microphone and the amplitude recorded. Hearing aids and hearing tests are improved on the basis of such experiments.