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[ShadowHammer]

I'm attempting to do a science experiment for a high school Physics class, and the idea is that I'll make and electromagnetic pipegun and then test how the projectile speed varies with current applied. Unfortunately, I've never done electrical stuff before, and know not very much about it This is further complicated by the fact that the gun gets plugged into a wall outlet, and I don't want to mess up my house's wiring or whatever.

So, I guess my main question so far is, how would I safely change the current without changing the voltage? And if anyone has any general electrical safety/working tips, those would be awesome too!

Spoiler: Extra Information (click to show/hide)

-The instructions I'm using for the gun:









-I was thinking, for the "safe" part of changing the amperage, that I could maybe just step-up it on the way "in" to the gun, and then step it back down on the way "out". I still don't know how to do that without changing the voltage, and actually I still don't know how to do that at all, so...

Thanks in advance!

[wierd]

That is what a transformer and some resistors are for.

A resistor resists electrical current flow, relative to a certain voltage.

Ohm's law is I=V/R

Or, Current, I, is equal to the Voltage, V, over the Resistance, R.

The corollary is V= R * I

So, for a given target voltage, you want a specific resistance, and a specific current behind it.

You can convert voltage and current interchangeably using a transformer. It's wasteful, but you could do a double transformer setup to get safe isolated power from the outlet, with suitable resistors at each part of the circuit.

Personally, I would look online for a good voltage regulator circuit designed for mains power. Many are available for free.

[Vector]

-snip-

[Amperzand]

This looks like a super neat school project.

[Catmeat]

Rubber gloves non conductive soles eye protection, get an extension cord go to the garage/shed/sleepout/bonghouse and becareful.
Also warn your closest neighbours as they may call the cops after hearing a loud bang and you screaming.
What is it. If im to cut a tree in 3 hours il spend 2 hours sharpening my axe.
Saftey first
And rifle the barrel

[ShadowHammer]

I tried this with a lawnmower battery once. Melted the gun and the wire, nearly set myself on fire. Electricity is not my friend.

...Sounds like fun!

Anyway, thanks for the help, everyone! I think Ohm's law there should fix this problem; if I just put a variable resistor into the circuit before the gun, I should be able to simply adjust the amperage by the inverse of the resistance without affecting voltage, right?
And if I do that, I'll just be decreasing the amps, so it should be safe to just plug right into an outlet without the whole "undoing" thing I mentioned, I think?
If that all works the way I think it does, then it looks like I'm set! I'm not actually making it until spring break, which is a couple weeks away, but I'll be sure to post an update here when I do!

[ShadowHammer]

It turns out that electricity does not, in fact, work the way I thought it did! Also, it turns out science is hard because real life has friction and stuff. I've decided to switch the test from how amperage affects things to how the number of coils does the same.

I now have a new problem related to the project: I want to be able to leave the gun in the "on" position for several seconds at a time, for force measuring purposes. This is problematic because an electromagnet is essentially just a short circuit. This is okay if I were to only leave it on for less than a second, but for continual operation, I think it's probably bad. Especially because it's plugged into a wall outlet.
Edit: apparently I'm wrong, and electromagnets aren't actually just dead shorts, apparently they produce significant impedance as well. Who knew? Anyway, the question's still relevant because there's still lots of current.

With that in mind, my new question for all you fine folks is, if I reduce the amperage of the circuit, will that make it safe for operating longer? And along with that, what's the best way to do so?
Edit: to clarify, what I'm really asking is, is amperage the bad thing? As in, if I have low amperage but high voltage, will it still fry the wires?

[Magistrum]

Electronic Technician here, want to try to help.
First: Yes, less current, less power, less heating, less exploding. But less fun, so there is that.

Second: Get yourself some good resistors. For 110V you will want a variable 10k and a 1k ohms(in series, so that minimum resistance is 1000) to change between about 1 ampere and 100 miliamper. Do keep in mind the rating of the thing: you need a resistor of minimum 10 watts! Those are only available as ceramic resistors, and I advise getting cooling on it if you are going to shot more than twice per minute.

Third: amperage is good. It is what defines the size of your wires. Voltage can be arbitrarily high and the wires will hold without problem while still carrying the extra potency. That's the reason land transmission lines are about 20kV.
 Edit: Oh, something important: Science really is hard, this thing will drain a hell lot of time from you and you will want to give up. Don't. You will succeed eventually.

[ShadowHammer]

Awesome, thanks for the help!