Tag Archives: Temperature

A2L Item 305

Goal: Unspecified.

Source: Unspecified.

Desert mirages are inverted images. From this, what can we conclude about the index of refraction of hot air compared to cold air?

  1. nHOT AIR > nCOLD AIR
  2. nHOT AIR + nCOLD AIR
  3. nHOT AIR < nCOLD AIR
  4. Mirages have nothing to do with refraction

Commentary:

None provided.

A2L Item 111

Goal: Problem solving

Source: UMPERG-ctqpe182

What temperature reading (if any) would have the same numerical value on
both the Celcius and Fahrenheit temperature scales?

  1. 0°
  2. -40°
  3. 180°
  4. 72°
  5. -25.6°
  6. 568°
  7. None of the above
  8. Cannot be determined

Commentary:

Answer

(2) This is a standard problem useful for determining whether students
are comfortable converting between the two temperature scales.

A2L Item 090

Goal: Reasoning about adiabatic expansion.

Source: UMPERG

An ideal gas is allowed to expand slowly. The system is thermally
isolated.

Which statement regarding the final temperature is true?

  1. T’ < T
  2. T’ = T
  3. T’ > T
  4. Not enough information

Commentary:

Answer

(1) For adiabatic expansion, TV(γ-1) is constant.
Since the volume increases, the temperature must decrease.

This result can be reasoned by considering the fact that work is done by
the gas. Since there is no heat transfer, the internal energy must
decrease. Since the internal energy of a perfect gas depends only upon
temperature, the temperature must decrease.

A2L Item 091

Goal: Hone the concept of internal energy and heat.

Source: UMPERG-ctqpe180

Body A has a higher temperature than body B. Which of the following
statements is true?

  1. Body A will feel hotter than body B.
  2. Body A contains more energy than body B.
  3. If placed in contact with each other, energy will flow from body A to
    body B.
  4. If placed in contact with a third body having temperature greater
    than body A, body B will absorb more heat than A.
  5. More than one statement is true.

Commentary:

Answer

(3) Only statement (3) is always true. Placed in contact, heat will flow
from the higher temperature body to the other regardless of the masses
of the bodies.

The ‘feel’ of a body’s temperature depends upon the material and the
rate of heat conduction. Body A could be much smaller than body B and,
therefore, contain much less energy than body B even though at a higher
temperature. Likewise, if body B is smaller it can absorb less energy
from a third body than body A even though it has a lower temperature.