left-hand rule
(also Fleming's left hand rule) Physics
noun
A mnemonic (proposed by J. A. Fleming (1849–1945), English electrical engineer), concerning the behaviour of a current-carrying conductor in a magnetic field, according to which the directions of the magnetic field, the current, and the force exerted on the conductor are indicated respectively by the first finger, second finger, and thumb of the left hand when these are held out perpendicular to each other.
Origin
1920s.