( ( This principle ) ( ( is ( used ( in ( making ( ( ( an electroscope ) , ) ( which ( is ( ( a ( scientific instrument ) ) ( that ( detects ( electrical charges ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT This) (NN principle)) (VP (VBZ is) (VP (VBN used) (PP (IN in) (S (VP (VBG making) (NP (NP (DT an) (NN electroscope)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBZ is) (NP (NP (DT a) (JJ scientific) (NN instrument)) (SBAR (WHNP (WDT that)) (S (VP (VBZ detects) (NP (JJ electrical) (NNS charges))))))))))))))) (. .)))
This principle is used in making an electroscope, which is a scientific instrument that detects electrical charges.
(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))))))) (. .)))