There are 3 bulbs in one room and 3 switches in another room.
Each bulb is connected to one of the switches.
you are in the room which has switches and all switches are initially in off position.
you can not see the light of another room.
How could you figure out which switch connected to which bulb by entering only one time into the room which has bulbs ?

Step1: Switch on the first switch and wait few minutes and switch off that. 
Step2: Switch on second switch and enter into the room. 
Step3: Touch all bulbs with hand. 
How to Figure:
1. Now the bulb which is giving light is connected to Second bulb.
2. The bulb which has hot temperature is connected to First switch.
3. The Other bulb is connected to 3rd switch.