If current always flows in the same direction, it is called a direct current. The current, which we get from the cell or a battery, is a direct current because it always flows in the same direction. The positive and negative polarity of a direct current is fixed. If the current changes direction after regular intervals of time, it is called alternating current. Most of the power stations in India generate alternating current. The alternating current produced in India changes its direction every 1/100 second. Thus, the positive and negative polarity of an alternating current is not fixed.