( ( ( Give ( the electroscope ) ) ( ( ( a ( positive charge ) ) , ) ( ( using ( the ( acrylic rubbed ) ) ) ( with silk ) ) ) ) . )
(ROOT (S (VP (VB Give) (NP (DT the) (NN electroscope)) (NP (NP (DT a) (JJ positive) (NN charge)) (, ,) (VP (VBG using) (NP (DT the) (JJ acrylic) (NN rubbed)) (PP (IN with) (NP (NN silk)))))) (. .)))
Give the electroscope a positive charge, using the acrylic rubbed with silk.
(ROOT (S (NP (DT A) (PRN (-LRB- -LRB-) (NP (NN n)) (-RRB- -RRB-)) (NN electroscope)) (VP (VBZ is) (VP (VBN used) (S (VP (TO to) (VP (VB study) (NP (NN charge))))))) (. .)))