Question

What is a choke coil

Answer 1

A choke is a wound coil generally used for smoothing or filtering the outputs from rectifying circuits. Impedance of chokeincreases with increase in frequency. Choke or coil is also used for RF filtering.

The choke coil can be used only in ac circuits, not in dc circuits, because for dc(ω=0) the inductive reactance XL=ωL of the coil is zero, only the resistance of the coil remains effective which too is almost zero.