Why does warm air rise during convection?
a. warm air is thicker.
b. warm air is less dense.
c. warm air is more dense.
d. warm air is more humid.

Two resistors r1 and r2 may be connected either in series or parallel across an ideal battery with emf ε. we desire the rate of energy dissipation of the parallel combination to be 8.75 times that of the series combination. if r1 = 105 ω, what are the (a) smaller and (b) larger of the two values of r2 that result in that dissipation rate?