Turn on the first switch and wait about half an hour, then turn it off.
Turn on the secound switch and go in the room right afterwards.
If the light is on, it's the secound switch.
If the light is off, check the bulp with your hands, if it feels warm it's switch number one, if it feels cold it's switch number three.

You coulnd't emagine it would be this easy, eh?

The riddle of the gates

This is the right question:
What gate your colleague would say is the right one?
Then take the other gate!

The bridge and the bomb

A + B cross the bridge = 10 minutes
A goes back = 5 minutes
C + D cross the bridge = 25 minutes
B goes back = 10 minutes
A + B cross the bridge = 10 minutes

Total time is 60 minutes

The long fuses

Okay, you need only two fuses.
Lit one fuse at both ends and the other one at one end at the same time. The first fuse will burn exactly half an hour, when it's all burned lit the other end of the other fuse. After exactly 15 minutes this fuse is burned too.