Direct current DC is one-directional flow of electric chargeAn electrochemical cell is a prime example of DC power. In alternating current the electric charge changes direction periodically. Why Is Ac Better Than Dc True AC alternates between a positive and a negative current flow like a pendulum and crosses zero volts twice per cycle or Hertz home current cycles sixty times per second or at 60 Hz while direct current only flows. . Direct vs alternating current. AC circuits as the name Alternating Current implies are simply circuits powered by an Alternating Source either voltage or current. Alternating current AC is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current DC which flows only in one direction. -- and can be converted to different voltages relatively easily using a transformer. But they are very different. High transmission and