2. How do the ancient Greek model and Ptolemy's model differ?

Greek's Model used stars while Ptolemy did not use stars.

Explanation:

The Greek model had stars as part of the system and they revolved around the Earth. Ptolemy's model did not include the stars, but it did include the moons that revolves around the planets.

a) the particles of the chair are strongly held together.

on passing the small ampere of electric current through the tube made of ar and hg of cfl generates uv rays which excites the fluorescent and thus emits the high radiation by consumption of just 5- 12 w in comparison to incandescent light which requires more power such as around 40 - 55 w to lighten.

moreover the life span of fluorescent or cfl is around 8000 h whereas the life span of incandescent is around 1200 h

hence, the building installed with incandescent lights bears more electricity bill.