henry (H) The unit of inductance of a circuit in SI units. The inductance of a circuit is one henry if the electromotive force (emf) in volts (V) is numerically equal to the rate of change in amperes (A) per second. Named after American scientist Joseph Henry (1797–1878), who discovered the phenomenon of 74570c08.qxd 9/11/07 12:22 PM Page 225 |