Unit zAh zeptoampere-hour Electric Charge A zeptoampere-hour (zAh) is a unit of electric charge used in the field of electricity and electronics. It is a derived unit that combines two base units: the zeptoampere (zA) for electric current and the hour for time. A zeptoampere (zA) is equal to 1 x 10^-21 amperes (A). An ampere is the standard unit of current in the International System of Units (SI) and represents the flow of electric charge through a conductor. An hour is a unit of time, equivalent to 3600 seconds (1 hour = 3600 s). When we multiply these two units, we get a unit for electric charge: zeptoampere-hour (zAh) = zeptoampere (zA) x hour Since a zeptoampere is equal to 1 x 10^-21 amperes, a zeptoampere-hour can also be defined as: 1 zAh = 1 x 10^-21 A x 3600 s = 3.6 x 10^-18 coulombs A coulomb is the standard unit for electric charge in the SI system. Therefore, a zeptoampere-hour represents a very small amount of electric charge, equal to 3.6 x 10^-18 coulombs. This unit is mostly used in applications, such as nano- and microelectronics, where extremely low electrical currents and charges are involved.