( ( ( ( Take ( a ( bar magnet ) ) ) and ) ( ( ( move it ) ( ( back and ) forth ) ) ( through ( ( the middle ) ( of ( the coil ) ) ) ) ) ) . )
(ROOT (S (VP (VP (VB Take) (NP (DT a) (NN bar) (NN magnet))) (CC and) (VP (VB move) (NP (PRP it)) (ADVP (RB back) (CC and) (RB forth)) (PP (IN through) (NP (NP (DT the) (NN middle)) (PP (IN of) (NP (DT the) (NN coil))))))) (. .)))
Take a bar magnet and move it back and forth through the middle of the coil.
(ROOT (S (NP (NNP Alternative) (JJ current)) (VP (VBZ is) (VP (VBN produced) (SBAR (WHADVP (WRB when)) (S (NP (DT a) (NN magnet) (CC or) (NN coil)) (VP (VBZ moves) (ADVP (RB back) (CC and) (RB forth)) (ADVP (RB repeatedly))))))) (. .)))