Direct vs Alternating Current

Watch the charges, the bulb and the graph

Peak current I₀ AC frequency (slow motion)

Current now0 A

Direction→

Effective (rms) value0 A

TypeDC

DC: charges drift in one direction only; current stays constant (battery, cell).
AC: charges move back and forth; current changes direction every half cycle.
I = I₀ sin(2πft), I_rms = I₀ / √2
In Pakistan, mains AC is 220 V, 50 Hz: the current reverses 100 times every second, too fast for the eye. Here it is slowed down.

Kamran Afsar Khan · Professor of PhysicsElectric Current