Contact electrical resistance of grade MPG-$7$ graphite at DC and AC current

The paper compares the values of contact resistance, which occurs when ac or dc current passes through one fixed contact surface. The comparison is done on MPG-$7$ graphite under identical experimental conditions. The temperature variation range was $350$–$750$ K. The voltage drop was measured with several point surface probes, which made it possible to simultaneously determine the contact resistance at different distances from the contact surface. It is shown that the contact electrical resistivity and contact resistance are higher when direct current is passed than when alternating current is used.