What are these cylindrical components on your laptop/camera power cord ??
These magical components are known as ferrite beads.
Why is it used ?
A long cable conductor acts as an antenna and has the capability to transmit/recieve unwanted signals ( most importantly radio frequency noise )
As an example, do you remember the annoying noise originating from your TV speaker while you were talking on your GSM mobile ? If yes, then it is nothing but your speaker wire acting as an antenna for mobile signals.
This little fella i.e ferrite bead is clamped over the current carrying conductor and it pretty much solves the high frequency problem.
It is very simple in construction and has a simple passive inductor made of ferritic material core (with ‘L’ as its inductance).
It offers resistance (actually reactance )to the high frequency signals and in turn dissipates the signal as heat.
The heat generated is not significant enough to bother you and this is how it solves the problem associated with radio frequency signals.