Question

A bell jar connected to a vacuum pump contains a partially inflated balloon. On creating a vacuum inside the bell jar, the balloon gets inflated. How does the pressure change inside the balloon and bell jar?
(A). Inside bell jar pressure increases
(B). Inside bell jar pressure decreases
(C). Inside balloon pressure increases
(D). inside balloon pressure decreases

Answer 1

Hint: The air around us exerts a pressure on every surface. The internal pressures of bodies and the atmospheric pressures must be equal to be in equilibrium. When the balance breaks, it is the tendency of every object in the universe to come back to its balanced state or equilibrium position.

Complete step-by-step answer:
Atmospheric pressure or air pressure is the force exerted per area by the air on a surface. We don’t feel the air pressure around us because the pressure of blood in our vessels cancels out the atmospheric pressure around us. Therefore to be in equilibrium, the magnitude of internal and external pressure must be the same.
This is clearly demonstrated by the balloon and bell jar experiment in which the bell jar is kept on a solid base and a vacuum pump is attached to it. A partially inflated balloon is kept inside the bell jar and then the vacuum pump used to remove the air completely from inside the bell jar to create a vacuum and leads to decrease in pressure inside the bell jar
As soon as the air is removed, there is an unbalance in the internal and external pressures of the balloon. As pressure inside the bell jar has decreased, air pressure around it is more. So, in order to balance the pressure differences in its surroundings, The balloon inflates which means pressure inside it increases.
Therefore, pressure inside the balloon increases and inside the ball jar it decreases. So, the correct options are (B) and (D).

So, the correct answer is “Option (B) and (D)”.

Note: As height increases the air pressure decreases, therefore sometimes at places at great heights, our ears tend to pop because due to decrease in external pressure, the pressure of the blood inside our bodies increases. Just like air, all fluids exert a pressure on the walls of its container and the bodies immersed in it.