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
Open-circuit voltage potential drop across the resistance C. The resistor B does not affect the open-circuit voltage. Since no current is flowing through it, there is no potential drop across it. So we can easily ignore it. Therefore, the potential drop across the resistance C is "V." This is just an example. Many other ways can be used. Open-circuit voltage Open-circuit voltage (abbreviated as OCV or V ) is the difference of electrical potential between two terminals of a device when disconnected from any circuit. There is no external load connected. No external electric current flows between the terminals. Alternatively, the open-circuit