Page 122 - Science Class 08

Aim : To show that the pressure of a liquid depends on the height of the column.
Method:
Take a plas c container and make three holes in it at different heights. Close these holes un l it
is not filled with water. Open the holes.

You will no ce that water comes out with greater force from the holes at less height. This shows
that the pressure in a liquid increases with depth.
It is a common property of all liquids that they find their own level.

Aim : To show that a liquid finds its own level.

Method :
Take three containers and connect them with a tube.
Close the joining tube in container un l it gets filled with water. Now, open the tube and allow
water to flow in other containers.

You will no ce that the level of water in all the containers is the same.
Therefore, we can say that a liquid finds its own level. The height of a water tank is decided on
the basis of the height of the houses in a par cular area, so that water can reach the houses of
the people.

Measuring Liquid Pressure
Liquid pressure is measured by an instrument called a manometer.

Let us make our own manometer through the given ac vity:

Aim : Making our own manometer.

Method :
Take a U-shape glass tube and fix it ver cally on a stand. Pour some water into the tube so that
both the drums of the tube have equal water level.
Close one end of the arm with a piece of polythene and a ach a rubber tube with the other end.
A ach the other end of the tube with a thistle funnel. Stretch and e a thin rubber balloon over
the mouth of the funnel so that the rubber remains constant. Now, the manometer is ready.

Let us test it. Press the rubber slightly with your finger. You will see that the level of water in
arm A falls and it goes up in arm B. The difference of the liquid levels in the two arms is a
measure of the pressure exerted on the rubber. We can now use it to measure the pressure of
liquid at different levels.

122 Science-8