Air Thermometer

Requirements  - A used electric bulb.  - A one-holed rubber stopper with a 60cm glass tubing. The stopper must fit tightly into the neck of the bulb.  - A candle.  - A wooden stand.  - A piece of paper.  - A bottle of water.  - A thermometer.  - Tacks and adhesives.  Procedure - Fit the stopper into the neck of the bulb. Seal it by dropping some wax from the candle around the joint. This is your thermometer.  - Paste the paper on the inside vertical face of the wooden stand.  - Colour the water inthe bottle with a little ink. Dip the glass tube of the thermometer in the ink-water.  -Fix the thermometer to the stand. - Now heat the bulb of the thermometer gently with candle to drive out some of the air. Drive out just enough air ensure that when the bulb cools to roomtemperature, the coloure water rise about half up the tube.  - To mark your scale, attach the other thermometer next to your air thermometer. Put the stand out in the sun for an hour.  - At the end of an hour make a line on the paper at the level of the water, and mark the reading of the thermometer at this point.  - Repeat above 2 steps an a cool, dark place.  - Divide the space between the two marks into equal divisions and marks off the corresponding temperatures.  Did you notice that this is an inverted thermometer ??