Explanation

[Electrostatic]

Can some one explain this problem to me. Im trying to see how to understand electronics in terms of real life and not just book problems. I understand the basics of what an inductor does but how can i apply the basics to this problem which is the following:

There is a BUZZ in your phone, which seems to go away when the battery is fully charged. You suspect the noise comes from an inductor in the phone's power supply. You open the phone, look at the power supply and see a ferrite core inductor: but some of the windings do not appear to be epoxied into place. Explain how this might cause the noise.

 

[Russlk]

Current thru a wire produces a magnetic field. Magnetic fields either attract or repel (in this case repel). If the current were DC, the wires would only change position but since it is pulsating DC, the wires repel and relax, causing the buzzing.

 

[me again]

In power work this phenomenon is simply called "noisy windings". A large transformer with loose windings can really make a racket. Windings can be quieted down by redipping and rebaking them to lock them in place.

 

[akg]

In power work this phenomenon is simply called "noisy windings". A large transformer with loose windings can really make a racket. Windings can be quieted down by redipping and rebaking them to lock them in place.

if magnetostriction is the problem as explained above .. then how come this ?
"There is a BUZZ in your phone, which seems to go away when the battery is fully charged. "
(as the voltage goes , some osc freq also goes down , which resonates with the ferrite core)