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
Lee Si-Chen of National Universities of Taiwan (2006 – ) and chair of the University Mobility in Asia and the Pacific (2005 – ). He is also a professor of electrical engineering at the National Taiwan University (1985 - ). He is interested in the scientific research of Chinese Qigong and extrasensory perception. Lee Si-Chen Lee Si-Chen (; born August 13, 1952 in Gangshan (岡山), Taiwan), is a Taiwanese engineer specializing in semiconductors, a researcher in amorphous silicon in the early development in Taiwan, and an IEEE Fellow. He has been a professor of electrical engineering since 1982 and the president of