Humming noise from an heater

[neo_star]

Why do we hear an humming noise when we switch ON a heater operated in AC.

 

[HarveyH42]

Would the hum be in the 60 Hz range?... Any chance you could send a sound sample? Fan type hum, or electrical?

 

[Mike_2545]

Is it a tune you recognize?

 

[Sceadwian]

It's probably a wound heating coil, the coils push against each other at the AC frequency. It's just like transformer hum from large power transformers.

 

[neo_star]

Would the hum be in the 60 Hz range?... Any chance you could send a sound sample? Fan type hum, or electrical?

i really dono but what do u mean by Fan type hum, or electrical.

 

[dknguyen]

If there are no moving parts in the heater (like no fan), the quiet humming that you hear is because the coils inside are expanding and contracting at 60Hz, as the 60Hz AC current flows through it. THat's why light bulbs, transformers, and power boxes seem to hum even though they have no moving parts.

 

[HarveyH42]

If there are no moving parts in the heater (like no fan), the quiet humming that you hear is because the coils inside are expanding and contracting at 60Hz, as the 60Hz AC current flows through it. THat's why light bulbs, transformers, and power boxes seem to hum even though they have no moving parts.

Aren't the coils moving?

 

[crutschow]

The sound is usually 120Hz (for a 60Hz line) since the coil contracts and expands from each peak to zero crossing.