IIT JEE Physics (1978-2018: 41 Years) Topic-wise Complete Solutions

Boyle's Law by Balloon in the Syringe

Objective

To verify Boyle's law.

Apparatus

disposable plastic syringe, balloon

Procedure

Take a large (30-40 ml) disposable plastic syringe. Remove its plunger. Blow a small diameter (\unit{1}{\centi\metre}) baby balloon. Put the baby balloon in the syringe tube. Insert the plunger. Close the nozzle of the tube tightly with your left hand finger and push the plunger slowly with the right hand thumb. The baby balloon will slowly shrink in size.

Now keep the nozzle closed and slowly retract the plunger. The baby balloon will slowly expand.

Discussion

When the balloon shrink in size, it shows that if the pressure increased inside the balloon its volume decreases. When the balloon expand, it shows that as pressure in the balloon decrease, its volume increases.

Hence, in both the cases $$pV$$ remains constant. Take care that temperature in the syringe remains constant.