Can you detect an Electric Line inside a wall?

Factual Questions
1

Regarding my post below about installing a light fixture, I did succeed however a small problem I did not anticipate did occur. The new light is rather heavy and it is only held by two small screws into the electrical box. The weight of the lamp is pulling the top of the base plate away from the side of the house about 1/4 of an inch. In my opinion it is a poor design because the light is heavy and the base is oval and the screws that hold it are at the bottom of the oval not at the center, it really needs to be secured at the top as well.

What I want to do is drill two new holes at the top of the base and place screws into the wall to hold the light more securely. What I am worried about is hitting the electric line coming down the wall to the electrical box and the switch. So is there any way to detect the electrical cable inside the wall? I don’t want to drill into the line. Any advice would be helpful.

http://boardstest.straightdope.com/sdmb/showthread.php?t=527302

2

You can detect a current carrying wire in a wall using a [tic tester](tic tester). This one is a bit pricey, there are cheaper ones available and there are stud finders that will detect conductors in walls. In my experience they work better when the circuit is energized.

3

If you’re going to drive screws to hold a heavy fixture, you have to drive them into a solid material, like wood. How much thickness of good wood (or whatever) do you have? Use screws of no more than that length. There’s no “holding” benefit to the screwthreads that go all the way through into the cavity where the cable is.