Metrication in the United States There are no U.S. customary units for electric current, potential difference, or charge since these concepts were developed after the international adoption of metric in science. The metric units ampere, volt, ohm and coulomb are the only units used. The SI term hertz has replaced the term "cycles per second" as a unit of frequency. Energy is often measured in watt hours, BTUs, therms or calories rather than the SI joule. Residential and commercial electrical energy use is metered and billed in kilowatt hours, kW·h, as in most metric countries. Force measurements regularly use the pound instead of the SI
Coefficients of potential Coefficients of potential In electrostatics, the coefficients of potential determine the relationship between the charge and electrostatic potential (electrical potential), which is purely geometric: where "Q" is the surface charge on conductor "i". The coefficients of potential are the coefficients "p". φ should be correctly read as the potential on the i-th conductor, and hence "formula_2" is the p due to charge 1 on conductor 2. or more formally Note that: The physical content of the symmetry is as follows: In general, the coefficients is used when describing system of conductors, such as in the capacitor. Given the electrical potential