The unit is volt . One volt is one joule per coulomb. A conductor allows electrons to pass with little loss of energy. Examples are metals, such as copper. An insulator does not allow electron to pass through.
Examples are plastics.
The unit is ampere, which is coulomb per second. Electric current can be produced by a chemical reaction, such as in a battery or with a mechanical generator. When a battery is connected to a bulb, the bulb provides the resistance, while the battery provides the potential. A typical frequency f in household current is 60 cycles per second, or 60 Hz. The power is the use of energy per unit time.