I am building an electrified "fence" of sorts to keep slugs out of my raised garden beds. The "fence" consists of two 18ga galvanized steel wires, stapled to wood and connected to a 9V battery. The circuit is open until the slug touches both wires, at which point he completes the circuit and gets a little shock. This works great in small scale tests, but my garden bed as a circumference of 30' (9.1 meters) and I'm concerned that a little 9V battery will have a hard time working at full power over that distance of wire.
Because I don't really know how resistance works (I just know how to get my volt meter to measure resistance so that I can make sure my solders are done well) I'm not sure how to do the math to see what kind of a drop in voltage I'm going to get.
If someone can answer this question directly, great. But I'd also love a website that I can use to help learn about this stuff.
- How can I find out the resistance of this wire? (Doesn't resistance change with voltage/amperage?)
- How does that resistance compound over distance?
- Are there simple parts (transistors, resistors, whatever) that I can go get at Radio Shack or the like that will help get over this resistance or should I just wire a second 9V battery into the system?
Bonus question: While 9V is a very light charge, if you imagine I'm building a much more powerful electric fence, what would I have to do to protect the battery if the circuit were completed for an extended period of time? (A slug dies on the line or something.) I wouldn't want some grass completing the circuit and having my battery explode.