Electricity most materials is relatively constant over a range of temperatures and currents; materials under these conditions are known as 'ohmic'. The ohm, the unit of resistance, was named in honour of Georg Ohm, and is symbolised by the Greek letter Ω. 1 Ω is the resistance that will produce a potential difference of one volt in response to a current of one amp. The capacitor is a development of the Leyden jar and is a device that can store charge, and thereby storing electrical energy in the resulting field. It consists of two conducting plates separated by a thin insulating
Ampere balance current. The main weakness of the ampere balance is that the calculation of the current involves the dimensions of the coils. So the accuracy of the current measurement is limited by the accuracy with which the coils can be measured, and their mechanical rigidity. A more complicated version of an Ampere balance, called the Kibble balance, that removes this source of inaccuracy by a calibration step was invented by B. P. Kibble in 1975. This experimental device is being developed at government metrology laboratories worldwide with the goal of providing a more accurate definition of the kilogram, the world's standard