The noisiness of materials for fixed resistors

Current noise in fixed resistors is usually expressed empirically in terms of current and resistance, but performance of different materials from which resistors can be constructed must be specified in terms of current density, resistivity and geometry. It is argued from the theory of dimensions that there should be a relationship between the index of frequency dependence and the index of resistance dependence. It is not clear how this can be associated with an experimentally observed relationship between frequency index and voltage coefficient. Secondary effects arise from any local concentration of current, and the order of magnitude of the associated temperature rise can be estimated from the potential difference across the contact by Holm´s theory of point contacts.