Note 1 to entry: At zero magnetic field strength and zero direct current, the superconducting condensation energy is given by $\left(1/2\right){\mu }_0{H}_{\mathrm{c}}^2$, where ${\mu }_0$ is the magnetic constant and $H_{\mathrm{c}}$ is the critical field strength.

Note 2 to entry: This entry was numbered 815-10-20 in IEC 60050-815:2015.