( ( ( An ( electric current ) ) ( passing ( through ( a metal ) ) ) ) ( ( consists ( of ( ( a flow ) ( of ( free electrons ) ) ) ) ) ; ) )
(ROOT (S (NP (NP (DT An) (JJ electric) (NN current)) (VP (VBG passing) (PP (IN through) (NP (DT a) (NN metal))))) (VP (VBZ consists) (PP (IN of) (NP (NP (DT a) (NN flow)) (PP (IN of) (NP (JJ free) (NNS electrons)))))) (: ;)))
An electric current passing through a metal consists of a flow of free electrons;
(ROOT (S (NP (NNP Metal)) (VP (VBZ conducts) (NP (NP (NN heat) (CC and) (NN electricity)) (ADVP (RB so)) (PP (RB well) (RB because) (IN of) (NP (JJ free) (VBG flowing) (NNS electrons))))) (. .)))