Unit of electric current.

Affected by the ampere in the 2019 redefinition of the SI base units.

TODO how does basing it on the elementary charge help at all? Can we count individual electrons going through a wire? www.nist.gov/si-redefinition/ampere/ampere-quantum-metrology-triangle by the NIST explains that is it basically due to the following two quantized solid-state physics phenomena/experiments that allows for extremely precise measurements of the elementary charge:

- quantum Hall effect, which has discrete resistances of type:
for integer values of $ν$.$R_{xy}=I_{channel}V_{Hall} =e_{2}νh $
- Josephson effect, which provides the Josephson constant which equals:
$K_{J}=h2e $