Electricians: Q on ending of Eight Legged Freaks (HUGE plot spoiler)

Factual Questions
1

I wanna make it clear that this whole thread is going to be discussing the ending of Eight Legged Freaks, a comic/horror movie about giant spiders that is currently out on video (BTW, three solid stars out of a possible four, IMO).

So anyway, if you don’t want to know how the humans defeat the giant spiders, hit the Back button now.

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Right.

The idea is that the spiders are all down in the mine tunnels, which are filled with methane, and there are large electric cables running power down into the mine tunnels. Apparently the power is not on, at this point in the story. The Hero breaks one of the light bulbs in the tunnel, sticks a book of matches in it, and tells the Heroine & Co. to go Up Top, find the generator, turn it on, and the power surge will ignite the matches, which will then ignite the methane.

So–wait, there’s more, my question isn’t just, “Would a power surge ignite a book of matches?”, although I wanna know that, too–anyway, when The Heroine & Co. get Up Top and find the generator, which is a display panel with some buttons and knobs and dials on it, they can’t get it to turn on, and the Kid announces, “It’s out of gas.” So they all look around desperately for gasoline, realize, “All these gas cans are empty,” and the Heroine says in despair, “All we need is one big electrical surge.”

So then the Teenage Girl realizes that she still has the stun gun in her pocket that she used to zap the Teenage Boy in the nuts earlier in the movie, but I digress…, anyway, she pulls out the stun gun, the Heroine applies it to the face of the generator somewhere, and KAPOW! The F/X kick in and we spend the next few minutes of screen time watching fiery explosions with flying CGI spider bodies.

So–would a standard-issue pocket-size stun gun have enough of an “electrical surge” to travel down a set of fairly hefty electrical cables into a mine and ignite a book of matches that were stuck in a broken light bulb?

And yes, yes, yes, (she said a trifle testily) I know that this is Only A Movie, and a Horror Spoof besides, and that there are many other plot holes even bigger than this (if the tunnels are filled with methane, how are all these people running around down there, for one thing), but I’m just curious about the stun gun.

2

IANAElectrical Engineer

I will say a stun gun certainly has the voltage. This one pops off 625,000 volts! However, I can’t imagine the amerage is anywhere near enough to send that juice very far down a power line. Still, all you theoretically need is a spark which theoretically should be enough to light a book of matches if. Why you need to light a book of matches and not just generate a spark I don’t know but hey…our hero needs to look clever so let him do his McGuyver thing if he wants.

3

Your average Tazer type gadget won’t put out enough power to handle the load of all the other lights and things on the cable and still push enough juice through the matches to light them. As far as that goes, putting the voltage that a light bulb runs on won’t win you any prizes, either. The voltage is too low to push enough current through the wood or paper of the match. You would need high voltage to do the trick - and if the voltage was that high, you’d just put a couple of wire ends close together and let a spark jump the gap which would then set off the methane.
BTW: a Tazer will probably set off a book of matches as long as the matches are all that gets zapped.

4

IANA “Electrician”.

  1. A stun gun has a voltage higher than the “break-down” voltage of the insulation between the conductors in the mine’s wiring.

  2. Even if (1) didn’t hold, the energy from the stun gun would be distributed between all of the lights, motors, etc. that were turned on in the mine. Think “trying to light all of the lights in the mine with a torch battery”.

So, no, it’s BS.

5

Desmostylus put the answer in simpler terms.
What they should have done was just bust a bulb and twist the wires inside it together and hten fire up the generator. The wires would have caused a short and melted and sparked and set off the methane.

6

IAAEE (I am an electrical engineer)

Which means that the energy just got grounded through the case of the generator and went nowhere. In order to get the electricity down the wires you’d have to be a lot more MacGuyver-ish about it, and you’d have to open up part of the generator to get to the wire connections, and then you’d have to find a couple of short pieces of wire to attach the electrical contacts of the tazer to them.

Assuming that you turned on the generator instead of using the tazer, I’m also having a bit of trouble seeing how the matches would even light, unless the person was VERY careful not to break the filament and made sure to leave the match head against the filament. Even then I’d say your chances aren’t all that great.

We keep a cattle prod in our office. I use it to keep the junior engineers in line (just kidding). Actually we use it just as a quick and dirty way of applying a nice electrical jolt to things. It can help find weaknesses in the design of things that control industrial processes, something I’m sure the cattle folks never imagined it would be used for. It’s very similar to a tazer, in that it gives off a nice electrical jolt. I’ve zapped ground wires and power supply wires and cases of all kinds of equipment, but it’s effects don’t go very far. The farthest I’ve been able to get it to do something was when I zapped a metal leg on an otherwise mostly wooden desk and caused a CD player on the other side of the desk to get really really confused. It made all kinds of weird noises like it was continually track seeking and coulding figure out where to place the laser. I was a bit worried that I had just bought my co-worker a new CD player, but it recovered when we cycled power on it.

Sensitive computer type parts (like the brain in a CD player) can get confused or damaged by a good zap like this, but you aren’t going to light a match or transfer any appreciable power this way.

7

Ah, lovely. Thank you, all.

I love this place. :smiley:

8

A match-head in contact with an unbroken light-bulb filament - even a flashlight-bulb filament - will flare right up when juice is applied to the filament. When I was younger and more foolish, I - uh, I knew this kid who did stuff like that. The setup, as you point out, is very delicate. But matches, after all, are intended to ignite when heated by a little friction. The light bulb filament gets quite hot - more than hot enough to light a match.

Not that there aren’t myriad other problems with the scenario in the movie, as you and others have pointed out.

9

What ECG said. And there whould be no need for the matches if the filament was unbroken and the glass broken and you could get ACTUAL power to it (It’s fairly impressive, actually).

If you know someone who owns one of those shockers, it shouldn’t be hard to try it on a light bulb. (Be careful!)

I think you’d see nothing but the arc. High voltage, tiny current.

10

But it was GREAT theatre !