Final answer:
In an AC circuit that contains only resistance, the current flow constantly changes direction. In a DC circuit that contains only resistance, the current flow is unidirectional.
Step-by-step explanation:
In an AC circuit that contains only resistance, the current flow is constantly changing direction as the voltage alternates. This is because AC, or alternating current, periodically reverses its direction. In a DC circuit that contains only resistance, the current flow is unidirectional and remains constant in one direction.