When considering a movable wire carrying an electric current or an electron beam within a magnetic field, a handy rule known as the left-hand rule, dynamo rule, or Fleming’s left-hand rule can be employed. By extending the thumb, first finger, and second finger of the left hand at right angles to each other, with the first finger indicating the direction of the magnetic lines of force and the second finger representing the direction of the electrons, the thumb then indicates the direction of motion of the wire or electron beam.