Out on an essential walk and I just walked under some power lines, why do they make that loud buzzing sound? Thank you!
In: Physics
Some power lines have pretty high voltage. It can be enough to cause corona discharges. They happen when the air ionizes and conducts current. Think of them as brief mini-lightnings. The sound is like a very weak but continuous thunder.
In transformers a reason is also because switching magnetic fields vibrate the components.
Makes a lot of sense, thank you!
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Modern power lines are “AC” or Alternating Current. This means it oscillates back and forth in the lines at 60 times each second.
Electric wires are magnetic, which means physical particles are are aligned in a certain way to make/interact with a magnetic field. Whenever the current changes direction, the tiny magnetic particles change direction as well.
Each cycle means two changes in direction. There are 60 cycles in a second, so all of the little particles vibrate at 120 hertz. They aren’t big enough to see, but they are definitely moving, and that many things vibrating in sync will make a 120hz sound.
They’re physically changing shape from the current flowing through them.
Most power lines are carrying AC at 50 or 60 Hz which means the current drops to 0 either 100 or 120 times per second. Every time the current ramps back up to a high value the flowing current creates a magnetic field which physically changes the shape of the wire, think of it like filling a hose with high pressure water how it’ll stiffen up. Now empty that hose and refill it again really fast and do that 100 times per second, you get a big hose that’s flopping about and making a lot of noise.
You’ll get really loud noise if you’re near a big transformer because there is an iron core inside of windings of wires which experiences a really strong magnetic field and will buzz because of that.
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