( ( ( ( ( We ( say ( that ( superconductors ( have ( zero resistance ) ) ) ) ) ) , ) but ) ( it ( might ( be ( more ( accurate ( to ( just ( say ( ( ( that ( ( ( Ohm 's ) law ) ( ( has utterly ) failed ) ) ) and ) ( that ( ( the resistivity ) ( simply ( ( is not ) ( defined ( for ( such ( a material ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (PRP We)) (VP (VBP say) (SBAR (IN that) (S (NP (NNS superconductors)) (VP (VBP have) (NP (CD zero) (NN resistance))))))) (, ,) (CC but) (S (NP (PRP it)) (VP (MD might) (VP (VB be) (ADJP (RBR more) (JJ accurate) (S (VP (TO to) (VP (ADVP (RB just)) (VB say) (SBAR (SBAR (IN that) (S (NP (NP (NNP Ohm) (POS 's)) (NN law)) (VP (VBZ has) (ADVP (RB utterly)) (VP (VBN failed))))) (CC and) (SBAR (IN that) (S (NP (DT the) (NN resistivity)) (ADVP (RB simply)) (VP (VBZ is) (RB not) (VP (VBN defined) (PP (IN for) (NP (PDT such) (DT a) (NN material))))))))))))))) (. .)))
We say that superconductors have zero resistance, but it might be more accurate to just say that Ohm's law has utterly failed and that the resistivity simply is not defined for such a material.
(ROOT (S (NP (NNS Superconductors)) (VP (VBP are) (NP (NP (NNS materials)) (PP (IN with) (NP (NP (DT a) (NN resistivity)) (PP (IN of) (NP (CD zero))))))) (. .)))