4 Switches and 4 Bulbs

Four switches that are downstairs control 4 bulbs that are upstairs in a room. You do not know which switch controls which bulb. You are presently at the downstairs. These four switches can be turned on or off. Once you do a combination of 'on and off', then you can go upstair and see the bulbs and should find it out which switch is for which bulb without coming back.

Answer:

Turn on switches 3 and 4 and wait fifteen minutes or so. Then turnswitch 3 off, turn switch 2 on, and enter the room. If the bulb is dark and cool, switch 1 controls it. If the bulb is bright and cool, switch 2 controls it. If the bulb is dark and warm, switch 3 controls it. If the bulb is bright and warm, switch 4 controls it.