Got shocked by touching screw on a light switch, please help!

I was just about to shut off the last light before existing my basement and my finger touched the screw of the light switch plate (plastic) and I got shocked. Tomorrow morning I plan open it up and look then go to homedepot & Ace to ask questions. I know almost nothing about electricity, except to practice safety.
Can anyone tell me what might be the problem before I start questioning other "electrical people". Thanks.

 

The screw is grounded, so it's not uncommon to get a static electricity shock from it. Is the basement carpeted? It's possible that there is no problem at all here. If you have no electrical experience, opening up the box might make things worse. Be careful.

 

I recently had to trouble shoot a similar situation.

A light switch on the outside of a closet with an upright freezer and refrigerator in it was shocking my daughter, but no one else.
After too thinking it was static, the problem kept re-occuring.
Turned out there was no ground on the older refrigerator and the compressor was failing causing the fridge to become electrically hot.

It seemed she had a habit of reaching in to the room to open the fridge and while holding onto the handle would then turn on the light and touch the plate screw.

 

The screw may not be grounded. In most places in the country grounding switches was not a common practice until 6 or 7 years ago. There very well may be 120 volts on the screw.

 

Thanks guys, still haven't looked at it. But the shock was pretty painful, it definitely wasn't a static electricity.

 

If you touch the screw and get a shock there has to be a place where the hot leg returns its potential through your body to ground.
It's very easy to troubleshoot.

If you are standing on a concrete floor in your stocking feet and only touch the screw to get a shock, then the switch box is ungrounded, the switch has failed and the screw is live.
If you are hanging on to something electrical while touching the screw then it is possible, as in my previous post, that whatever electrical device you are touching has become live and the screw is returning current to ground.

So, if you are only standing on a concrete floor and get a shock you have to replace the switch and would do well to rewire the box to include a ground to make your wiring safe.

Make sure you turn off the breaker and check for power with a reliable tester before you work on it or call a qualified electrician.

 

Here is one of the brands of tester that may help in finding which surface is actually energized.
http://www.tooled-up.com/Artwork/ProdZoom/SEAAK1998.jpg
http://www.tooled-up.com/Product.asp?PID=109037
http://www.tooled-up.com/Artwork/Pro...ak1998test.jpg

Here is another.
http://www.mytoolstore.com/ideal/ide05-14.html

If a device such as these is tested at a known working receptacle and then shows voltage on the plate screws that would indicate that there is a fault between the ungrounded current carrying conductor and the strap of the switch either directly to the strap or to the Equipment Grounding Conductor (EGC) that is connected to that strap with an open or high impedance connection somewhere in the EGC between the fault and the main bonding jumper in the service equipment enclosure.

If such testing does not reveal any elevated voltage on the device strap then the energized surface is nearby and the plate screws are serving as the return pathway for the stray current.
--
Tom H