Ciro Santilli
🔗

# 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? https://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 extremelly precise measurements of the elementary charge:
• quantum Hall effect, which has discrete resistances of type: $$Rxy​=Ichannel​VHall​​=e2νh​ (1)$$ for integer vallues of .
• Josephson effect, which provides the Josephson constant which equals: $$KJ​=h2e​ (2)$$
🔗
🔗

🔗