Heat & Work

Problems

practice

  1. Write something.
  2. Write something else.
  3. Write something different.
  4. Write something completely different.

conceptual

  1. Three unrelated questions about ceiling fans.
    1. A ceiling fan in a closed room (or even one with poor ventilation) does not make the room cooler. It actually increases the temperature of the air it pushes (not significantly, however). Why does this happen?
    2. What does a ceiling fan do that would make people think (under certain circumstances) that it cools a room?
    3. In really large heated spaces, ceiling fans are used to make the space occupied by people feel warmer. (This is a completely unrelated phenomena to the one described in part a.) Why does this happen?
  2. A thought experiment. Two perfectly insulated, rigid chambers of identical shape and size are place side by side with a narrow opening connecting the two. The opening is initially blocked. One chamber is filled with a gas and the other contains a perfect vacuum. The opening is then unblocked. Determine the sign of the following quantities for the gas …
    1. the heat released
    2. the work done by the gas
    3. the change in internal energy and temperature
  3. Two related questions.
    1. Can a gas absorb heat without getting hotter? If so, how is it possible? If not, why is it impossible?
    2. Can a gas absorb heat and not expand? If so, how is it possible? If not, why is it impossible?

The Physics Hypertextbook

  • No condition is permanent.