In A.C circuits electrons move back and forth and the net current over one complete cycle is zero.Then how does a bulb connected to an AC circuit glow as the same number of electrons flowing in flows out at next instant?
When the light bulb is connected to AC circuit, electronsare moving in the filament. Filament has high temperature. Electrons move back and forth, but electrons move forth - stop - move back. Before the electrons change direction, electrons has moved slow. So, current is less. But we can't see this process. Why? Because filament has a thermal inertia, and light bulb can't cool down in a split second.