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# For science fiction writings, I want to accurately portray railguns

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For science fiction writings, I want to accurately portray railguns and the math behind them. Could I get layman explanations of electrical terms and measurements? Volts, amps, joules, etc. Joules, if I understand correctly, are equivalent to kinetic energy, but everything else I don't understand at all.
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>>7636532
Imagine that electricity is water or some other incompressible fluid, flowing down a pipe. The water molecules are actually electrons.

Voltage, measured in Volts, is the pressure in the pipe. The voltage difference between two points is a measure of how much energy it would take to move a charged object between those points - or how much energy would be released by letting it move the other way. (Moving an electron across a voltage of 1 Volt takes exactly one electron-Volt (eV) of energy, for instance).

Current, measured in Amperes, is the ... current. It's the rate at which electrical charge is flowing through the wire in a given moment; the derivative of electrical charge with respect to time.

Like with water currents, if you multiply the voltage (pressure) by the current, you get the power carried by the electricity. Power in electricity is measured with the same units you measure power anywhere else - Watts.

A Watt is one Joule per second; Joules are the generic metric unit of energy.
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>>7636554
Thank you, that helps a lot.
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>>7636554
Doesn't pressure in water pipes increase flow-rate though?
Also how do you make sense of spark gaps with this analogy?
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>>7636575
Dont take it to literally. It works nothing like hydraulics, its just an easy analogy to visualise what is happening in a circuit diagram
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>>7636575
In reality, the electron isn't actually really going anywhere, it is transferring energy to an electron in the atom next to it via photonic exchange. The voltage is the cost of the exchange
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>>7636575
>Doesn't pressure in water pipes increase flow-rate though?

Yes. If you have a higher voltage running through the same wire, you'll get a higher current.

The law relating them is Ohm's Law, I=V/R. The current flowing through a wire (Current gets the symbol I. Don't ask why.) is equal to the voltage across the wire, divided by the resistance of the wire.

Resistance is how "resistant" an object is to electrical flow, and thus how much voltage you need to force some amount of current through it. Resistance is measured in Ohms.

>Also how do you make sense of spark gaps with this analogy?

A spark gap is a capacitor: Two electrodes separated by an insulating layer.

Think of a capacitor as a stretchy rubber membrane in the middle of the pipe. As you increase the voltage, the pressure pushes harder and harder across the membrane, and a charge develops across the capacitor - you get more water on one side, and less on the other side. This also stores energy, because of the tension in the membrane, and if you give it a chance the capacitor will discharge and release that energy.

The higher the capacitance, the bigger the charge difference you can build up before the voltage gets too high, and thus the more energy you can store.

What do I mean about the voltage "getting too high?" Well, think about it - if you stretch that membrane too much, it'll break, and electricity will flow freely through the pipe. This is called the "breakdown voltage." In air, this happens through forming sparks - if the voltage between the gaps is too high, then despite the resistance of the air, the electric field will be strong enough that electrons will start jumping the gap. This creates an arc of ionized gas - and because ionized gas (plasma) is much more conductive than ordinary air, current can now flow directly across and all the stored energy in the electric field discharges at once.
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>>7636575
>>7636608
>>7636622

>In reality, the electron isn't actually really going anywhere

This is a subtlety I didn't quite point out, yeah. In electrical circuits, the electrons themselves are hardly moving at all - less than a millimeter per second. But because one electron pushes on the next, which pushes on the next, etc, in an almost totally incompressible fashion, the actual flow of electricity is very rapid.
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>>7636622
>Yes. If you have a higher voltage running through the same wire, you'll get a higher current.
Hm, what about transformers and such though? Don't they work with the same wire?
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File: 1389510696272.jpg (21KB, 222x220px) Image search: [iqdb] [SauceNao] [Google]
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>>7636622

>Current gets the symbol I. Don't ask why

I for intensitĂ¨.

The intensity of the current.

Blame the French
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>>7636649
AC electricity runs on somewhat different rules.
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>>7636649
Any current generates a magnetic field around it, and there is some energy stored in that field. Transformers put energy in with one set of windings and take it out with the other (kind of sort of, we're still in 1000-foot-view land). Railguns put a bunch of energy into a magnetic fieldâ€” the rails+armature are a giant 1-turn inductorâ€” and then extract that energy mechanically by allowing the loop area to increase.
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>>7636629
At the speed of sound?
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The most important part here is to apply as large current as possible. The voltage drives the current and the resistance is, at least initially, low.

The power source, the two rails and the armature make up one single turn coil. As long as the armature shorts out the rails the loop exists.

Applying a current, preferably an absolutely enormous current, sets up a correspondingly large magnetic field flowing through the loop. The field interacts with the current carrying parts but only the armature is made to be able to slide. The Lorentz force applies a force sliding the armature forward, accelerating as it slides. The force and thus acceleration (F = M a) persists until the armature escapes off the rails.
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>>7636608
Is this true? If this is the case, what constitutes directionality?

This is why mathematics has become science's cancer. Even introductory electrical engineer, or basic physics books are so heavy with unnecessary "plug blah blah into the equation, now you know all you need about the mechanics of the material you're working with! Eventually everyone will be a mathematician and understanding reality through strictly mechanical, physical, or spatial means will be obsolete! B-T-DUBS, want to build a bandpass filter? Well, you can do it like this, and with this equation you can figure the balance of your circuit. Might be good to go into how different materials respond to varying frequencies... like ferrite inductors becoming permanently magnetic after being saturated... but nah. There's an equation someone's worked out for you for everything! Don't waste your time building some silly bandpass filter, there are plenty that are well documented and available for purchase! Engineering is like legos now, embrace this!" Gee, thanks.

Fucking thanks, 90% of textbooks out there. Took me ages to find one written by someone who actually tells the reader things they need, and in my case actually want, to know. This goddamn planet, sometimes I wonder if my way of comprehending is all fucked up, or the rest of your's is. Mathematics is a tool to use, it isn't a substitute for knowing what's happening. When it has served its purpose or led to experimental data, the ideal is for it to be stripped, and thrown away.
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>>7636532
Basically, you'd have to magnetize the nucleus of the atom with a few anti particles, finding the stability sector isnt the easy part, and have that be the casing for the electrons to replace the nucleus of the shrodong effect of the new nucleas, which would basically be like 1/3 to 1/5 of the amount of nuetrons in the given power source being used with anti nuetrons
>???
>Destruction