( ( ( use ( ( an understanding ) ( of ( ( conductors and ) insulators ) ) ) ) ( to ( explain ( in ( terms ( of ( electrons ( what ( happens ( when ( objects ( are ( ( ( charged ( by ( ( ( ( ( friction , ) contact ) , ) and ) induction ) ) ) or ) ( grounded ( by touching ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) . )
(ROOT (S (VP (VB use) (NP (NP (DT an) (NN understanding)) (PP (IN of) (NP (NNS conductors) (CC and) (NNS insulators)))) (S (VP (TO to) (VP (VB explain) (PP (IN in) (NP (NP (NNS terms)) (PP (IN of) (NP (NP (NNS electrons)) (SBAR (WHNP (WP what)) (S (VP (VBZ happens) (SBAR (WHADVP (WRB when)) (S (NP (NNS objects)) (VP (VBP are) (VP (VP (VBN charged) (PP (IN by) (NP (NP (NN friction)) (, ,) (NP (NN contact)) (, ,) (CC and) (NP (NN induction))))) (CC or) (VP (VBN grounded) (PP (IN by) (NP (VBG touching))))))))))))))))))) (. .)))
use an understanding of conductors and insulators to explain in  terms of electrons what happens when objects are charged by friction, contact, and induction or grounded by touching.
(ROOT (S (NP (NNP Grounding)) (VP (VBZ is) (SBAR (WHADVP (WRB when)) (S (NP (PRP you)) (VP (VB touch) (NP (DT a) (JJ charged) (NN object)) (PP (TO to) (NP (DT the) (NN earth))))))) (. .)))