SI unit of electric potential difference (voltage)
one volt = one joule per coulomb of charge
named after Alessandro Volta, inventor of the first chemical battery
drives electricity (current) through conductors: V = I * R (Ohm's law)
household mains: 120 V (Americas) or 230 V (Europe, Asia)
single cell battery: 1.5 V (alkaline), 3.7 V (lithium-ion)
lightning: hundreds of millions of volts
neural action potentials: ~70 mV resting, ~+40 mV peak