Hey All,
A friend of mine asked me why there was an audible hum from his flourescent light. I know that the noise from a bad flourescent light ballast is from the 60 hertz AC electronics. However, I was unable to convice him of how that actually makes a sound that we can hear? I mean, there aren’t any moving parts that cause the air to vibrate.
Thanks in advance for your help,
-Sand Writer
There are parts moving to create the sound (as there must be)- the wires themselves. The AC current in the wire (most likely in the ballast) creates a magnetic field around the wire- basically an electromagnet. This causes an attraction between one piece of wire and other pieces of wire. Since the field is expanding and collapsing in sync with the AC voltage, this causes the wires to vibrate at that frequency, as they are attracted (or repelled) and released in step with the varying voltage.
This is also the reason a large power transformer will hum- the magnetic field is varying with the voltage, and causing the wires to physically move as the field pushes/pulls on them.
Arjuna34