why freezer present on top inside of the refrigerator? why heat coils present at the bottom of geyser?

IN REFRIGERATOR

In the freezer, once air gets cooled the internal molecules of air comes closer and becomes heavier once air molecules become heavier it moves from top to bottom by making cool entirely in the fridge. also, air conditioner works on the same principle.

IN GEYSER

once water gets heated from bottom molecules will move away from each other by releasing heat energy thereby same water becomes light in weight. as it is light it floats upwards thereby making complete water evenly heating.

• light air goes upwards
• heavier air comes downwards