Nonlinear and Negative Resistance in Loose Electrical Contacts Dark Bridge

Abstract

The dark bridge in loose electrical contacts was investigated, which grew up when the contact gap was increased a little with micron by micron. The dark bridge was watched by microscopic camera along with measurement of voltage-current (V-I) relationship. At very small gap (less than 19µm for iron (Fe) contacts but different from materials), the V-I characteristics were linear, which is normal, but more than the 20~30µm, the non-linear relationship appeared and finally the negative resistance was observed. Experimental growth of dark bridge was shown in case of Pd. The nonlinear and negative resistance phenomena were tested for Fe. The resistance was analyzed and showed that it goes to negative one after crossing zero from positive region.