OP said the at-fault driver's insurance is offering the deductable&rental and asking OP to report the accident to his/her own insurer for all further costs. That sounds perfectly OK

>each of those signal wires needs only to be shorted to the power to close the circuit and activate a particular function.

 

Yes, exactly (I do not know what two-stage is, so likely I over-simplified something).

For years, here in England, I was frightened to mess with landine phone circuits until I noticed that all the wires excpt two are just snipped off.

 

By the way, by contrast, the thing a home user (here) should never try to mess with is ordinary electrical power sockets, because they have an unbelievably subtle configuration. All the live, neutral, and ground wires are connected in a intentional circles called 'ring mains' (with redundancy and an intentional ground loop) so you can depend on how it will work even if any wire is cut, and, secondly all the neutral wires and all the ground wires are connected together...but they are connected outdoors. Even before RCD there were almost never any fatalities because of this strange system. So for example, with two leads coming into a house, to connect two sockets, you need nine wires, with most in parallel with other wires, where only six, or actually four, would suffice. I won't try to explain the theory behind this but it is non-trivial. Essentially, neutral and ground are two independent versions of ground that are redundant but isolated from each other in such a way that significant current cannot flow between them without being noticed at the fusebox.

 

Another weird thing is, the ground wire of an electrical shower was bare, but covered by a decorative green/yellow striped tube which did not totally cover it. This meant, because of having that large bare wet electrical wire next to you, you were sure you were completely safe. And, it worked. Where, back in the USA with half the voltage (one-quarter the power into any given resistance) there was actual significant danger just because of people mowing their lawn or trying to install an electrical shower when users were allowed to wire things up. They may still have those polarized but ungrounded plugs which go in either way, but you have to press harder to get them to go in with the reverse polarity.

 

Actually, that is a sense in which any of the wires to the boiler/furnace could, in the USA, be dangerous because the ground of the furnace/boiler could well be live compared to the ground of some other room. Something that would be dangerous but you'd never notice it without stretching a wire between the rooms for some purpose.

I agree with RobBears. Many thermostats just act as a simple switch, in that case all that matters is which two wires actualy go to the furnace, and not which order. I note online that red is usually the low voltage (typically 24V) power supply input to the thermostat and the white is the output wire from the thermostat back to the furnace that calls for heat, with yellow and green not actually connected to any part of the heating system. So for many thermostats, all they do is connect the red wire to the white wire when the room is below the target temperature and disconnect if the room is above it. I'd imagine for some solid state thermostats the polarity might matter. Then you'd want not to interchange red and white. I note some online diagrams say a thermostat can sometimes independently control a fan of the furnace or air conditioning. In my country I've honestly never seen that, because the PCB of the boiler is more intelligent and more apt to know when it wants the fan running or not, and because maybe we worry about carbon too much to run air conditioners from a thermostat; but anyway in that case, either the green or yellow wire would be connected to terminals on the heating/AC system and when needed is ALSO shorted, by the thermostat, to the red wire. Even if you mess up and accidentally connect the wires wrong it will not cause any damage to your furnace/boiler/AC because some thermostats in some situations under normal operations actualy will connect all the wires together; and the only risk would be if you reverse polarity you might damage a solid state thermostat if you attach the red wire to the wrong terminal of the actual thermostat.

>polarity shouldn't make a difference since it's just a magnetic pull

 

Good point, the math for that isn't as simple as saying when the current reverses so does the force....it would if the projectile were permanently magnetized (and that were the significant effect) but it is just iron and its own magentization is caused by the coil and reverses too. If that did happen, one could try to tune the circuit to oscillate just once and pull the projectile partway then push. But as you say, by the time the projectile is at the midpoint one wants to have the current shut off.

First comment is to be very careful, the current those capacitor could put through a human body at 400 volts is very very far above lethal.

 

Second comment is, a resistor is going to drag down the cicruit and dissipate a lot of your energy. You know that the rate of change of current at the start, at time zero, is voltage divided by inductance, V/L. So at the beginning the graph of current over time looks like an increasing line of slope V/L. The total charge that has flowed is the integral of this which is 1/2 (V/L) t^2 if t is time. But then the voltage starts to decrease, the voltage is Q/C where Q is charge, and at the outset Q=Q_0 - 1/2 (V/L)t^2 where Q_0 is starting charge. The best way to continue is by differential equations because V is not really constant, but for small values of time, if we approximate the charge that has flowed as 1/2(V_0/L)t^2 where V_0 is initial voltage, then remaining charge is Q_0 - (1/2)(V_0/L) and voltage is V= (1/c) (Q_0 - (1/2)(V_0/L)t^2) so in this formula Q_0 is starting currentm V_0 is starting voltage and you see the voltage dropping off. It is clear that you need to increase L. As I say, this is just an approximation for small time.

 

By the way, you would also see if you write down the differential equation, an oscillation after the bullet has left. If you had an amazingly durable diode you could prevent reverse flow, but I do not know how expensive it would be to get a diode that can handle the very extreme currents you'd want to put through it.

 

You can see that you have a small coil --- that is the problem.

Nice thing to do. I did think at first you meant this https://www.youtube.com/watch?v=RGBZ3IH3sYI which needs a spring compressor and a ball-joint fork.