An observation of the breaking arc between silver contacts using a high speed color video

The distributions of a spectral intensity of the breaking are between silve r contacts in DC 45-66 V/2.5-5.0 A circuits have been measured using a high -speed color video. As a result, a cathode brightening spot, which has a hi gh spectral intensity, exists near the cathode surface. The cathode brighte ning spot expands with the increase of the contact gap, but its length expa nds until about 180 mu m. When the contact gap spreads over about 180 mu m, a dark positive column appears and grows between the cathode brightening s pot and the anode surface. The higher the interrupted current is, the large r the diameter of the cathode brightening spot will be. The maximum diamete r of cathode brightening spot is 500 mu m under these experiments.