Q: Why is there a thick plastic part on the head of the computer cable?
Answer: The end of a computer cable has a part that looks like a plastic cylinder. It seems like a simple thing but it does a very important job. Due to the continuous flow of two different charges inside the cable, there is a disturbance in the electromagnetic field. As a result some noise is generated. If the charge enters the computer with this noise, it can damage some sensitive parts of the computer. So to eliminate the noise from the flowing charge, there is a cylinder-like part near the connector at the end of the cable, which is called a ferrite bead. It contains ferrite (a compound of iron oxide and ceramic) powder. This ferrite bead acts as a conductor, preventing very high frequency (5-100 MHz) noise from reaching the connector. As a result, the computer stays safe.