In order to clarify the physics of contact life time, the relationship between heat capacity of holder and shape of bridge (length and diameter) is discussed in this paper. The AgPd60 alloy is chosen as electrode material. Two holders with different heat capacity are comprised of copper plate and cylinder. The shape of the bridge at the low speed breaking contact is observed by using the high speed digital camera. It was demonstrated that the shape of the bridge is changed by the response and distribution of the temperature.

It is necessary to know how the contact voltage and contact area vary with time to clarify the physics of contact lifetime and contact resistance. In this paper, to clarify the effect of the heating value on the diameter of the contact area, the variations of the contact voltage and contact diameter with time are measured at a low-speed breaking contact near the thermal equilibrium condition under which a stable bridge is generated. The effect of the heating value on the relationship between the contact diameter and the length of the bridge at breaking is also discussed. In the results, the contact voltage waveform was found to be macroscopically proportional to the displacement of the moving electrode lc. On the other hand, the contact diameter dc decreased slightly with increasing lc. At all currents investigated dc decreased when lc increased. The length of the bridge at breaking was increased by increasing the current. A large heating value of the contact area resulted in a long bridge because the volume of the melted metal increases.