# Why Power Lines Buzz: Explaining the Motor Principle

• physicsgal
In summary, the buzzing sound that is often heard near high-voltage power lines is most likely caused by the resistance of the power lines.
physicsgal

## Homework Statement

explain why high-voltage power lines give off a buzzing sound using what you know about the motor principal to explain the source of the buzzing.

## Homework Equations

so the motor principal has to do with when a force is exerted on a current-carrying conductor when it is in a magnetic field.

## The Attempt at a Solution

the field lines changed their shape (or position) and this causes a frequency that produces sound?

any help is appreciated!

Amy

I googled to check, and both effects that I suspect are discussed in this thread:

The one I'm most familiar with is corona discharge, especially on a wet/humid day. The 60Hz power waveform produces 120Hz peaks in voltage, and the 120Hz buzz is very audible.

The the thread I linked to also discusses the effect that you are being asked about in your question. To help you get farther -- calculate the force on typical high voltage power transmission wires. That force will also peak at a 120Hz rate in the US. Use the typical spacings and voltage and power levels for a transmission line to see how much deflection you might get in the wires.

thanks. I am still not sure how to word my answer so it relates to the motor prinicipal though.

Amy

Can you define what is meant by "the motor principal"?

Do you know how to calculate the force on current-carrying wires that are in a magnetic field? Do you know how to calculate the magnetic field generated by current carrying wires? Do you know how those effects are used in electric motors?

Can you define what is meant by "the motor principal"?
when a conductor carries a current at right angles to a magnetic field experiences a force at right angles to both the current and the direction of the field.

Do you know how to calculate the force on current-carrying wires that are in a magnetic field? Do you know how to calculate the magnetic field generated by current carrying wires? Do you know how those effects are used in electric motors?
theres been no calculations so far. I am just suppose to give my best reasonable guess about the cause of the buzzing sound.

Amy

What course is this for? Is there a later chapter in your book that describes the magnetic field? In most introductory E&M books, in the middle of the first chapter on the magnetic field, they show how forces are generated between parallel current carrying wires. If you have a text like that, look ahead a little to get a better picture of what is going on. The currents flowing in the power transmission line generate AC magnetic fields, which interact with the currents in the wires to generate some forces.

They are working on Grade 11 Physics. I had the same question when I was doing a correspondence course through www.ilc.org (Ontario, Canada).

I'll take a look at answer I provided when i get home. One thing though, I do remember when I mentioned the 60 Hz buzz peaking at a rate of 120Hz the teacher incorrectly changed the figure to 60Hz. Sometimes you just can't win... =)

In my text, the very next chapter actually mentioned what causes the buzz, maybe you will be equally as luckly...

Last edited:
thanks. his is just an introductory hs course. nothing fancy. here's what i wrote:

When a current flows through a conductor, it creates a magnetic field. This field interacts with the field produced by the magnets. These fields fluctuate, and cause the current to interact with the wires of the power lines. This leads to resistance, which causes some of the electricity to be lost as heat and sound energy (buzzing).

Amy

thanks ND3G. the last chapter does relate the buzzing to the resistance. ) This chapter doesn't mention any math involved (no 60 hz or anything)

Amy

physicsgal said:
thanks. his is just an introductory hs course. nothing fancy. here's what i wrote:

When a current flows through a conductor, it creates a magnetic field. This field interacts with the field produced by the magnets. These fields fluctuate, and cause the current to interact with the wires of the power lines. This leads to resistance, which causes some of the electricity to be lost as heat and sound energy (buzzing).

Amy

Just a brief clarification. The "magnets" part would apply to many actual motors, but not to the powerline example. The magnetic field from one line interacts with the electrons flowing in the other line to generate a force on the other line, and vice-versa. It will make a lot more sense when you get to studying magnetic fields in detail in college.

thanks again

Amy

## 1. What is the motor principle?

The motor principle is a fundamental concept in electromagnetism that explains how electric currents can produce rotational motion in a magnetic field. It is also known as the motor effect or the Lorentz force, named after the scientists who first described it.

## 2. Why do power lines buzz?

Power lines can produce a buzzing sound due to the motor principle. As electricity flows through the power lines, it creates a magnetic field around the wires. When this magnetic field interacts with the Earth's magnetic field, it can cause the wires to vibrate and produce a buzzing noise.

## 3. How does the motor principle work?

The motor principle works by using the Lorentz force, which states that a charged particle moving through a magnetic field experiences a force perpendicular to both the direction of motion and the direction of the magnetic field. In the case of power lines, the electric current acts as the charged particles and the Earth's magnetic field acts as the external magnetic field, causing the wires to vibrate and produce rotational motion.

## 4. Can the motor principle be used for other purposes besides power lines?

Yes, the motor principle has many practical applications in various devices, such as electric motors, generators, and even particle accelerators. It is a crucial concept in understanding and harnessing electromagnetism for technology and engineering.

## 5. Is the buzzing sound from power lines dangerous?

No, the buzzing sound from power lines is not dangerous. It is simply a byproduct of the motor principle and does not pose any health risks. However, if the buzzing sound is accompanied by other issues like flickering lights or power outages, it is best to contact a professional to inspect the power lines for any potential hazards.

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