Pick out the WRONG statements about magnetic substances. ( = magnetic susceptibility) ( _r = relative permeability). I. Substances with -1 II. Substances with 1 are paramagnetic. III. Substances with 1 are ferromagnetic. IV. Substances with _r 1 are ferromagnetic.

Step-by-step solution

For diamagnetic substances, the magnetic susceptibility is small and negative, so -1 For paramagnetic substances, is small and positive, so 0 For ferromagnetic substances, is very large and positive, so 1 . Statement III states 1 , which is incorrect. For ferromagnetic substances, the relative permeability _r = 1 + . Since 1 , it follows that _r 1 . Statement IV is correct. Therefore, statements II and III are wrong. Answer: II and III