Tesla query--simple case, but

So why did this one break? http://tinypic.com/r/2vlofuh/9

It's not illuminated--is it? Or do the lamps behave differently than the squares?

The Tesla puzzle has only one solution and whenever you place a lamp that would leave you unable to complete it, the puzzle will break. In this example, the broken lamp should have been beneath the 1-battery instead of next to it. Because you placed it somewhere else, it became impossible to light all tiles and therefore it broke.

The two yellow dots had to be bulbs as the left one of the two stations with two batteries on them only had two available tiles where bulbs could be placed. The pale yellow lines show which tiles would have been lit up as a result.

This then meant that the tile with the black dot could only be illuminated with bulbs placed on either tile with a red dot, as it could not be a bulb itself (the right 2-battery station already has the two yellow bulbs). Placement of a lamp on either red dot meant the tile SE of the 1-battery station had to be a bulb. (pink lines show which tiles the red bulbs would have illuminated)

Hope that makes sense.

Simply - The battery needs one bulb next to it. This is only to be treated as a clue. Each time you place a bulb it effects several other cells around it. To be successful, pay attention to what the bulb does to other cells when you choose to place it :)

Thank to both of you! To arrrrt for stating a non-obvious principle, "It breaks now because it knows it will have to later", and to Severine for clearly applying it.