My physics assignments in class!! Enjoy :)

1. CHAPTER 3.3 GAS PRESSURE

2. GAS PRESSURE
 Force per unit area exerted by the gas
particles as they collide with walls of the
container.

3. Kinetic Theory of Gases
• Discrete. • Moves freely in random
motion.

4. Kinetic Theory of Gases
• Kinetic energy increases with the
temperature.

5. Kinetic Theory of Gases
• Collisions with each
other and the walls of
the container are
elastic.
• Forces of attraction
NEGLIGIBLE.

6. ATMOSPHERIC
PRESSURE
 It is a thick layer of air that surrounds the
earth.
 It occurs when gas molecules collides to
each other in the atmosphere and an
object.
 It acts in all direction.
 The value of atmospheric pressure is
about 1.0 x 105 N m-2 or 1.0 x 105 Pa.

10. INSTRUMENTS FOR MEASURINGGAS
PRESSURE
U-tube manometer
Bourdon gauge

11. U-TUBEMANOMETER
The gas whose pressure is to be measured is
connected directly to one side of the U-tube.
The pressure of the gas is equal to the sum of
atmospheric pressure and the pressure due to
the difference in the height of the liquid in the
manometer.

12. BOURDONGAUGE
Commonly used in school laboratories, air
conditioner service shops, hospitals and factories.
When a Bourdon gauge is attached to a gas cylinder,
gas flows from the cylinder into the flattened
curved tube in the gauge.
The pressure of the gas causes the curved tube to
straighten out.
Through a lever and a gear system, the pointer
rotates to measure the pressure of the gas.

13. INSTRUMENTSFOR MEASURINGATMOSPHERIC
PRESSURE
oMercury barometer
oFortin barometer
oAneroid barometer

14. MERCURYBAROMETER
Made by inverting a long glass tube filled with
mercury.
Due to the inversion, a vacuum is created at the
base of the tube and a column of mercury is
supported by the atmospheric pressure.
The units for the measurement of atmospheric
pressure can be in terms of centimeters of mercury
(cm Hg) or Pascal (Pa). Another unit of pressure is
torr, where 1 torr is equal to 1 mm Hg.

15. FORTINBAROMETER
• Essentially modified from a simple mercury
barometer.
• The Fortin barometer has a metal scale with a
vernier attached and a mirror behind the top of the
mercury column to avoid parallax error when taking
readings.
• With these features, the Fortin barometer measures
the atmospheric pressure more accurately than the
simple mercury barometer.

16. ANEROIDBAROMETER
 More convenient form of barometer because it
does not use liquid and can be as small as a
wristwatch.
 Inside an aneroid barometer there is a partially
evacuate metal case made of thin and flexible alloy.
 A change of atmospheric pressure will cause the
centre of the metal case to move in or out. This
movement is magnified by a system of levers.
 A chain attached to the last lever rotates the
pointer to show the atmospheric pressure
measured.

17. THE END !
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