The measure of the pressure difference of electricity (EMF or ElectroMotive Force). The pressure required to force one ampere of current through a resistance of one ohmohm. The flow of voltage is called current. In electrical devices, there is a possibility of both AC and DC voltage. DC voltage is produced by a battery or power supply. AC voltage is from the electric company or a power source or power supply. Extra high voltage (EHV) is any quantity over 345,000 volts. Ultra high voltage (UHV) is referred to any amount in excess of 800,000 volts.