Question

Fig. shows two air filled bulbs connected by a U-tube partly filled with a light oil.
(a) How does the levels of oil in limbs X and Y change after the electric bulb is lighted.
(b) Give reason for answer in part (a).

Answer 1

a) The level of oil in $X$ decreases and in $Y$ increases.

b) When the electric bulb is lighted; as black body absorbs and radiates more heat, so in $X$ side more vapours will be formed due to which pressure is increased in $X$-side and due to this level of oil in $X$-side is decreased and in $Y$-side it is increased.