Some questions about Power Supply Adapter

In fact, the sizzling sound in the power adapter is the sound of the inductance coil vibrating due to the action of the magnetic field when the alternating current passes through. The inductance coil is generally packaged with enamel, epoxy resin, heat shrink tape, etc. Generally, if the enameled wire is wound and packaged, It   can be well sealed to isolate the sound generated by the vibration of the inductive coil.

Power Adapter

If the sound of the power adapter fluctuates when it is working, it may be that the upstream device of the inductor is short-circuited. In this case, danger may occur, such as a short circuit in a notebook and a spark at the plug. Of course, it is impossible. .
First of all, under normal circumstances, when the notebook power adapter is powered on, it will make a faint sizzling sound, which is the sound of electric current.
However, if the zigzagging sound is very loud, or it will be loud for a while and then small for a while, it is likely that there is a problem with the equipment. The manufacturer of the power adapter has summarized   two situations for you.
1. The Power Supply is unstable. The power adapter is actually a transformer. When converting the power supply, it will emit a sound with a fixed frequency. If the power supply is unstable, the sound from the inductance coil will be different.
2. The connection plug of the adapter is not tightly inserted, the connector is too loose, and the contact is poor, resulting in a large resistance, and the sizzling sound will also increase accordingly.
3. The inductor coil is generally packaged by varnish, epoxy resin, heat shrink tape, etc., which can protect  the circuit and isolate the sound of the current. The sound of the electric current is naturally louder.