( Then ( ( that ( electrical energy ) ) ( ( is ( ( converted ( to ( light energy ) ) ) ( by ( the bulb ) ) ) ) . ) ) )
(ROOT (S (RB Then) (NP (DT that) (JJ electrical) (NN energy)) (VP (VBZ is) (VP (VBN converted) (PP (TO to) (NP (JJ light) (NN energy))) (PP (IN by) (NP (DT the) (NN bulb))))) (. .)))
Then that electrical energy is converted to light energy by the bulb.
(ROOT (S (NP (DT A) (JJ light) (NN bulb)) (VP (VBZ converts) (NP (JJ electrical) (NN energy)) (PP (TO to) (NP (JJ light) (CC and) (JJ thermal) (NN energy)))) (. .)))