1. A goose-neck style lamp.
  2. An extension cord.
  3. Different wattage of incandescent light bulbs - 25 watt, 40 watt, 60 watt, 75 watt, 100 watt, 150 watt.
  4. Compact Fluorescent light bulbs - 7 watt, 23 watt - They are expensive; so shop around for ones that don't cost so much.
  5. Thermometer.
  6. A ruler or yard stick to measure distance from the thermometer to the light bulb.
  7. A white towel.
  8. A watch or stop watch to measure the time.
  9. A piece of paper and pencil to record your observations.
Put the towel on a flat table.

Put the goose neck lamp on the end of the towel on the table
Put the thermometer under the light of the lamp and measure the distance from the bulb.
Make sure the lamp is unplugged and screw in the smallest wattage light bulb
5. Measure the temperature and write down the start temperature
Angle lamp over thermometer and turn on lamp.
Leave lamp shining on the thermometer for at least five minutes
Start watch and at the end of five minutes read the temperature and mark down what the final temperature is.

Repeat the steps above with each different light bulb.

  • Allow the lamp and desk to cool for half an hour between each bulb.
  • Do not unscrew the light bulb right after turning off the lamp as the bulb may be hot and can burn you.
  • Unplug the lamp before changing the bulb.
  • Make sure the distance between the thermometer and the light bulb is the same for each different bulb. The thermometer should be in the same spot.
  • The starting temperature for thermometer should be about the same for each light bulb.

Incandescent lights give off heat as well as light energy. The higher the wattage of the light bulb the higher the temperature. A compact fluorescent bulb gives off very little heat energy because they do not use resistance and cause a light to glow hot.

In a home or office, lots of incandescent lights means that the air conditioner would have to use more energy during the summer to remove the extra heat given off by lights. Also, some lights such as torchieres, can be very dangerous as the bulbs are rated at 300 watts or more and get VERY hot. They can catch drapes or other materials on fire if you're not careful.


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