( ( An electroscope ) ( ( is ( ( a device ) ( that ( detects ( electrical charge ) ) ) ) ) . ) )
(ROOT (S (NP (DT An) (NN electroscope)) (VP (VBZ is) (NP (NP (DT a) (NN device)) (SBAR (WHNP (WDT that)) (S (VP (VBZ detects) (NP (JJ electrical) (NN charge))))))) (. .)))
An electroscope is a device that detects electrical charge.
(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))))))) (. .)))