what is the use of plastic bundles around computer data/power wires?

Question

Just around the plug end there will be large cylindrically stuffed bundle

Answer 1

These cylinders are "chokes" made of Ferrite.

Their purpose is to cancel electromagnetic interference.

If you have a cable and a current is running through that cable, the current is creating a magnetic field.

Normally, in a cable there are two lines, with power running in one direction in one line and in the other direction in the other line thus canceling out the magnetic field.

However if you have Power running through a cable and this current is grounded through another cable, this will create an electromagnetic wave, if the current suddenly changes.

This will interfere with sensitive devices like TV's Radios or generally all devices that somewhat react to electromagnetic interference.

By using a Ferrite choke, you create a coil, that dampens this interference.

Answer 2

Usually it is like a cylindrical bundle at the end, near the connector?
This is a coil of wire, and it helps prevent electrical magnetic inteference along the wire.

These are especially used with computer equipment, as the devices are highly sensitive to interference, such as Monitors and Scanners.

Answer 3

Most likely, they are the terminating ends of the strands used for stress relief in the entire cable length. Use of conductors only have no strength if cable is pulled or twisted. The plastic strands pick up the strain.