5. The charge on a glass rod which has been rubbed with silkis called positive: A) by arbitrary convention B) so that the proton charge will be positive C) to conform to the conventions adopted for G and m inNewton's law of gravitation D) because like charges repel E) because glass is an insulator 5. The charge on a glass rod which has been rubbed with silkis called positive: A) by arbitrary convention B) so that the proton charge will be positive C) to conform to the conventions adopted for G and m inNewton's law of gravitation D) because like charges repel E) because glass is an insulator