Which statement relates most directly to the second law?
1 - thermal energy is conserved.
2 - some thermal energy is lost and some is used to do work.
3 - thermal energy flows from areas of higher to lower temperatures.
4 - thermal energy can be transferred and transformed.

Option (2) is the correct answer.

Explanation:

According to second law of thermodynamics, all the energy of a system cannot be converted into useful work because some amount of energy will be lost.

For example, a machine will never convert its energy into 100% work as some of the energy of machine will be lost into the atmosphere.

Therefore, we can conclude that the statement some thermal energy is lost and some is used to do work, relates most directly to the second law.

the duration of a photographic flash is related to an rc time constant, which is 0.100 μs for a certain camera.