- #1
sandman18and5
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First Post!
So I was curious about how I could relate my new found knowledge of electromagnetic inductance on guitar pickups and I came across this on the internet:
http://www.sciencebuddies.org/science-fair-projects/project_ideas/Music_p004.shtml#background
Which says, "All of these magnets are surrounded by a coil of very fine magnet wire containing thousands of wraps. When a steel string on the guitar vibrates, it perturbs the field of the magnet just beneath it. This changing magnetic field induces a current in the coil of wire. With a properly designed pickup, the perturbations in both the magnetic field and the current in the coil are synchronized with the vibration of the string. When the signal from the pickup is amplified, it produces the sound of the electric guitar."
I find conflict with this. Here is how i would describe a pickups mechanism. Please fill in any holes in my understanding:
So what I think is happening is that the magnetic field is pointing perpendicular to the plane that the strings are vibrating in. This creates a current in the guitar string. A guitar string then has it's own magnetic field created by it's current. This brings us to Faraday's law stating that the Change in the Magnetic Flux over time is proportional and opposite in direction to the induced EMF/current. When this string moves back and forth over thousands of coils of copper wire, it's small magnetic field generates a current big enough to be sent to an amplifier to amplification. So I think that the string's vibrating source of a changing magnetic field is what creates the change in the flux in the coils. There is no CHANGE in flux given by the magnetic field generated by the Neodymium magnet, or so I believe.
A bit more in depth, I think that not only the fact that the string has it's own magnetic field determines the sound, but it also has to do with the mechanical wave propagating through it. When the string moves to the right over a upward magnetic field, the current in the wire propagates backward by the right hand rule. When going to the left, the string creates a current going forward through the string. This creates clockwise and counter-clockwise magnetic fields. So, I postulate that the induced current in the pickup is Alternating Current! The frequencies of the mechanical waves propagating through the string are reflected in the frequencies of the induced current, which allow it to retain its musical characteristics like frequency. Also, I've noticed that if you pluck a string harder on an electric guitar, it sounds louder on an amplifier. I think this is because the velocity of each infinitesimal part of the string is greater, which increases the current, thus increasing the strings magnetic field, thus making a stronger induced EMF.
Something I'm blurry on:
- how does the magnetic field cause a current in the string in the first place? I'm not sure if F = qv x B or more appropriately F = Idl x B.
The law of Biot and Savart may apply if I knew if/why current was going through the strings.
- people on the internet keep saying that since the string is a conductor, it distorts the magnetic field of the natural magnet thus creating a flux in the coil. How much truth is there to this?
So I was curious about how I could relate my new found knowledge of electromagnetic inductance on guitar pickups and I came across this on the internet:
http://www.sciencebuddies.org/science-fair-projects/project_ideas/Music_p004.shtml#background
Which says, "All of these magnets are surrounded by a coil of very fine magnet wire containing thousands of wraps. When a steel string on the guitar vibrates, it perturbs the field of the magnet just beneath it. This changing magnetic field induces a current in the coil of wire. With a properly designed pickup, the perturbations in both the magnetic field and the current in the coil are synchronized with the vibration of the string. When the signal from the pickup is amplified, it produces the sound of the electric guitar."
I find conflict with this. Here is how i would describe a pickups mechanism. Please fill in any holes in my understanding:
So what I think is happening is that the magnetic field is pointing perpendicular to the plane that the strings are vibrating in. This creates a current in the guitar string. A guitar string then has it's own magnetic field created by it's current. This brings us to Faraday's law stating that the Change in the Magnetic Flux over time is proportional and opposite in direction to the induced EMF/current. When this string moves back and forth over thousands of coils of copper wire, it's small magnetic field generates a current big enough to be sent to an amplifier to amplification. So I think that the string's vibrating source of a changing magnetic field is what creates the change in the flux in the coils. There is no CHANGE in flux given by the magnetic field generated by the Neodymium magnet, or so I believe.
A bit more in depth, I think that not only the fact that the string has it's own magnetic field determines the sound, but it also has to do with the mechanical wave propagating through it. When the string moves to the right over a upward magnetic field, the current in the wire propagates backward by the right hand rule. When going to the left, the string creates a current going forward through the string. This creates clockwise and counter-clockwise magnetic fields. So, I postulate that the induced current in the pickup is Alternating Current! The frequencies of the mechanical waves propagating through the string are reflected in the frequencies of the induced current, which allow it to retain its musical characteristics like frequency. Also, I've noticed that if you pluck a string harder on an electric guitar, it sounds louder on an amplifier. I think this is because the velocity of each infinitesimal part of the string is greater, which increases the current, thus increasing the strings magnetic field, thus making a stronger induced EMF.
Something I'm blurry on:
- how does the magnetic field cause a current in the string in the first place? I'm not sure if F = qv x B or more appropriately F = Idl x B.
The law of Biot and Savart may apply if I knew if/why current was going through the strings.
- people on the internet keep saying that since the string is a conductor, it distorts the magnetic field of the natural magnet thus creating a flux in the coil. How much truth is there to this?