I was wondering, how do pickups work, exactly? I heard pickups are usually just magnets that sense how far the strings are and how they move when you play and based on that, they send that info to the amp.

Is that true? Would you be able to do harmonics on pickups? What about if you changed out your strings, would you hear that through the amp, or would it simply detect the notes you are playing and present them with a typic guitar sound through the amp.

I guess this may be a better way of explaining what I am asking...
If you, for instant, used two different guitars with the same pickups, would the two guitars sound different or exactly the same?

Thanks. I know so very little about electric acoustics but they are really starting to interest me!
There are lots of factors that affect guitar tone, like string gauge, string age (how long since you changed them?), scale length, pick type/age, wood, and action. So no.
You may have had this in high school: moving a magnet inside a copper coil gives a small voltage over the two ends of that wire, but only as long as the magnet moves. The same happens in a guitar, but instead of moving the magnet you move the magnetic field around.
The magnets in the pickup emit a magnetic field that exits the magnet at the north pole, loops around the magnet and enters through the south pole. However, this is only true for a magnet in air.
Different substances have different magnetic permeabilities (the substance's desire to conduct magnetism). Your steel guitar strings have a much higher one than the air around them, so they kind of 'curve' the magnetic field in an odd shape so it passes through the string, and not the air around it. When you pluck the string, it carries the magnetic field along with it while it vibrates, giving the same moving magnetic field as in the magnet in the copper coil. This gives a small AC voltage where the frequency is dependent on the frequency of the string. Amplify this signal through your amp, and you can crack the walls and shake the ground.
Quote by Xtinct Dark
You may have had this in high school: moving a magnet inside a copper coil gives a small voltage over the two ends of that wire, but only as long as the magnet moves. The same happens in a guitar, but instead of moving the magnet you move the magnetic field around.
The magnets in the pickup emit a magnetic field that exits the magnet at the north pole, loops around the magnet and enters through the south pole. However, this is only true for a magnet in air.
Different substances have different magnetic permeabilities (the substance's desire to conduct magnetism). Your steel guitar strings have a much higher one than the air around them, so they kind of 'curve' the magnetic field in an odd shape so it passes through the string, and not the air around it. When you pluck the string, it carries the magnetic field along with it while it vibrates, giving the same moving magnetic field as in the magnet in the copper coil. This gives a small AC voltage where the frequency is dependent on the frequency of the string. Amplify this signal through your amp, and you can crack the walls and shake the ground.

This. The best way to think of them is like little microphones that amplify your strings vibration when plugged into an amp. You can also have active pickups which use batteries. Typically most pickups are passive however.

I've built pickups out of phone magnets and copper craft wire. It's an interesting way to understand the construction and designing of pickups.
Wow, thank you all very much! Extremely interesting and detailed, but I think I understand what you are talking about.

Phew, I was worried I would lose effect by recording with pickups, but it looks like that will not be an issue. I guess I was comparing it to MIDI. I am not sure if you guys have ever used MIDI, but you can play an extremely out-of-tune piano that has MIDI, and when your computer gets that information, it just plays what notes were played on the piano, leaving out the piano's own tone and tune, so what you played out-of-tune would then be recorded as in-tune. So, really, you are just telling your computer what notes to play and how fast, hard, etc., but it is the computer that determines the sound.
I am glad the guitar picks are not like that.

I have one more question... I have never used amps, pickups or USB interfaces, is there anything I should know so as to not damage anything? Things need to be plugged in while powered off, lower volume when plugging in, anything random like that that I may not do that might mess up my instrument or gear?

Thanks soooo much!!!
Practically the only safety procedure I go with is when you set up a new rig, or completely alter your amp an guitar volumes, you got to start with every volume knob turned to its minimum to prevent you from hearing damage should you max out your volume somewhere.
Some people say it's advisable that you should turn down all your volume knobs to prevent the loud bangs when you switch off your gear, but I never do that. I experienced just the same amount of bangs with and without the volumes turned down, so I figured it doesn't matter.

When switching on your righ (amp, pedal, ax etc.), start from your guitar and work your way up throug the signal chain (first connect guitar, switch on pedal, siwtch on amp) but leave the guitar's volume down. After you set up you can turn your guitar's volume up and you're good to go.

When switching off, go the other way around (amp first, then pedals and then guitar) to avoid the real bad bangs from your amp. Especially when you unplug a pedal's power from the socket you can create enormous sparks along th plug and get enrmous voltage surges along your signal chain that can really damage your amp. It doesn't happen often, but don't push your luck.
WOW! Great tips! Thank you very much! :]
Quote by Isakale
Wow, thank you all very much! Extremely interesting and detailed, but I think I understand what you are talking about.

Phew, I was worried I would lose effect by recording with pickups, but it looks like that will not be an issue. I guess I was comparing it to MIDI. I am not sure if you guys have ever used MIDI, but you can play an extremely out-of-tune piano that has MIDI, and when your computer gets that information, it just plays what notes were played on the piano, leaving out the piano's own tone and tune, so what you played out-of-tune would then be recorded as in-tune. So, really, you are just telling your computer what notes to play and how fast, hard, etc., but it is the computer that determines the sound.
I am glad the guitar picks are not like that.

The reason for all this is because MIDI is not an audio (sound) signal; MIDI is a computer language used by devices that can understand MIDI, to tell each other when to play a note/sample, how loud to play it (velocity), how long to play it for, and whether it needs to be modified (pitch bend, for example) as well. When you play a MIDI instrument, you are just inputting data which other MIDI devices can read. When this data reaches a MIDI-equipped keyboard, or a software instrument in a DAW (recording program), it is used by the device/program to play the data you have created through this system and output a sound.

I have one more question... I have never used amps, pickups or USB interfaces, is there anything I should know so as to not damage anything? Things need to be plugged in while powered off, lower volume when plugging in, anything random like that that I may not do that might mess up my instrument or gear?

Thanks soooo much!!!

Just follow the setup instructions in the manual of any gear you buy, and you should be fine, or ask in our Official Recording Chat Thread if you get stuck. It's hard to give rules that work for everything, but as Xtinct Dark said - try to picture the signal flowing along the chain of devices and you should be able to understand where any problems are occurring as you check each device in the chain. The advice on keeping volumes switched to their lowest is also very good practice to get into - it is very easy to have something blast out at ridiculous volumes if you aren't careful with audio equipment, and whether it was caused by loud gigging before I was sensible enough or not (hard to say as there are a few potential causes for mine) I have tinnitus and it isn't something I would wish on anybody, even if mine is fortunately under control and something I've managed to adapt to so far.

As far as breaking anything, the most common risk with recording guitars is if people don't keep their amp hooked up to the speakers (if it's a combo amp, this only applies if they've disconnected the speakers it comes with) and plug the main power amp output into anything else. As long as you're sensible and understand that your amp's output has to see the correct impedance whenever the amp is turned on, unless the amp's manual explicitly says you can turn the output off for recording, or it can blow up the amp and devices it is plugged into!
Hey, look. Sigs are back.
Thanks!