( ( ( Electrical current ) ( ( ( whose direction ) ( of flow ) ) ( ( does not ) reverse ) ) ) . )
(ROOT (FRAG (NP (NP (JJ Electrical) (NN current)) (SBAR (WHNP (NP (WP$ whose) (NN direction)) (PP (IN of) (NP (NN flow)))) (S (VP (VBZ does) (RB not) (VP (VB reverse)))))) (. .)))
Electrical current whose direction of flow does not reverse.
(ROOT (S (NP (VBG Alternating) (NN current)) (VP (VBZ is) (NP (NP (DT the) (NN term)) (PP (IN for) (NP (JJ electric) (NN current))) (SBAR (WHNP (WDT that)) (S (VP (VBZ keeps) (S (VP (VBG reversing) (NP (NN direction))))))))) (. .)))