[1] When is heat engine called reversible? Show that all reversible engines are equally efficient.
[2] Calculate the action between two small magnets of moments and
placed in one line, the centers being at a distance
from each other.
[3] What are the characteristics of and
rays from radioactive substances?
[4] Calculate the velocity of sound in hydrogen at by the formula
where
the velocity of sound in air at
,
, the coeff of thermal expansion,
,
being the density of hydrogen relative to air.
