Unit ZAs zettaampere-second Electric Charge Unit zAs, or zeptoampere-second, is a unit of electric charge in the field of electricity and magnetism. It represents a very small quantity of electric charge and is derived from the units of electric current (ampere) and time (second). A zeptoampere (zA) is an extremely small unit of electric current, equal to 10^-21 amperes. It comes from the SI prefix "zepto-" which means 10^-21. Similarly, a second is the SI unit of time. To obtain the electric charge, we multiply the electric current by the time for which it flows. Therefore, a zeptoampere-second (zAs) is equal to 10^-21 amperes multiplied by 1 second. In terms of the unit of electric charge, coulombs (C), 1 zAs is equal to 10^-21 C. The zAs is a very small unit of electric charge, and it is used for expressing extremely low amounts of electric charge in scientific contexts. It is somewhat impractical for everyday use as the charge would be too small to be measured accurately. But within certain fields such as nanotechnology, quantum physics, or other areas dealing with minute charges, using zeptoampere-second as a unit can be more convenient.