A partially inflated balloon is placed inside a bell jar connected to a vacuum pump. On creating vacuum inside the bell jar, balloon gets more inflated. How does the pressure change: increase, decrease or remains same, inside the (a) bell jar and (b) balloon ?

(a) On creating vacuum inside the bell jar, the pressure inside it decreases due to the absence of air.

(b) The pressure inside the balloon remains the same as the amount of air inside the balloon does not change. The reason the balloon gets more inflated by creating a vacuum inside the bell jar is that due to the vacuum, the air surrounding the balloon has been removed so the pressure surrounding the balloon has decreased. But the air inside the balloon keeps pushing at the same pressure causing the balloon to inflate further.