Dependences of arc duration D and contact gap at arc extinction d on contact opening speed v are studied for break arcs generated in a 48VDC resistive circuit at constant contact opening speeds. The opening speed v is varied over a wide range from 0.05 to 0.5m/s. Circuit current while electrical contacts are closed I0 is varied to 10A, 20A, 50A, 100A, 200A, and 300A. The following results were obtained. For each current I0, the arc duration D decreased with increasing contact opening speed v. However, the D at I0=300A was shorter than that at I0=200A. On the other hand, the contact gap at arc extinction d tended to increase with increasing the I0. However, the d at I0=300A was shorter than that at I0=200A. The d was almost constant with increasing the v for each current I0 when the I0 was lower than 200A. However, the d became shorter when the v was slower at I0=200A and 300A. At the v=0.05m/s, for example, the d at I0=300A was shorter than that at I0=100A. To explain the cause of the results of the d, in addition, arc length just before extinction L were analyzed. The L tended to increase with increasing current I0. The L was almost constant with increasing the v when the I0 was lower than 200A. However, when I0=200A and 300A, the L tended to become longer when the v was slower. The characteristics of the d will be discussed using the analyzed results of the L and motion of break arcs. At higher currents at I0=200A and 300A, the shorter d at the slowest v was caused by wide motion of the arc spots on contact surfaces and larger deformation of break arcs.