# Electric current - High voltage power lines buzzing

1. Jul 23, 2012

### alicia113

Electric current -- High voltage power lines buzzing

Question:

High voltage power lines string along roads often give off a faint buzzing sound. Use what you know about the motor principle to explain the source buzzing.

ok, so i have no idea how to approach this. I've never heard the buzzing around high voltage lines, but i am guessing it has something to do with the metal around it? i dont really know can someone please help me !!!

2. Jul 23, 2012

### truesearch

Re: Electric current

do you know how an electric motor works.... current in a wire in a magnetic field moves !!!
Power cables have AC current flowing in them, The current creates magnetic fields,... does this give any clues?

3. Jul 23, 2012

### alicia113

Unfortunately no :( ok in going to take a guess here the current moves on way and the electro magnetic field hits other wires causing them to vibrate ?

4. Jul 23, 2012

### Staff: Mentor

Re: Electric current

You are close to correct in your guess, at least with the question worded the way it is. There can be two sources of noise from HV powerlines -- the electromechanical effect that you are trying to describe, and a more common one that is more apparent in wet weather:

http://en.wikipedia.org/wiki/Corona_discharge

To better describe the electromechanical effect, does your textbook describe the Lorentz force at all? How about the forces between parallel wires carrying currents?

5. Jul 23, 2012

### alicia113

Re: Electric current

Nope nothing It's out home summer school course and each unit/lesson is about 6 to 7 pages of information so there's nothing on it

6. Jul 23, 2012

### Staff: Mentor

Re: Electric current

What level in school is this? Is it high school or first year college? Have you had trig? How much calculus have you had?

The wikipedia page on the Lorentz force has several levels of math explanations...

http://en.wikipedia.org/wiki/Lorentz_force

(and scroll down to the section on "Force on a current carrying wire"...)

7. Jul 23, 2012

### Staff: Mentor

Re: Electric current

Hmmm, I´d never thought of the motor principal being involved in power line hum, not even in a tiny way. It would be interesting to determine whether the contribution by this means is discernible.

Though the premise itself is sound*.

‡ no pun intended
* ditto

8. Jul 23, 2012

### alicia113

High school grade 11. It is an at home physics course so I'm teaching myself. So it's hard. And ok will do. I'll check it out and post later what I get!

9. Jul 24, 2012

### alicia113

Re: Electric current

do you think what i said earlier would be correct in some ways?

10. Jul 24, 2012

### Staff: Mentor

Re: Electric current

Sure.

Are you getting close to being able to answer the question in your post #1 here?

Perhaps you are not sure what is meant by the motor principle? Well, it relates to wires carrying electric current. If these conductors are near each other, the magnetic field around each will cause an attraction (or maybe repulsion) by the other.

Last edited: Jul 24, 2012