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INTRODUCTION
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| Gases are bad conductors of electricity. However under reduced pressure and at high potential difference gases conduct electric current. | |||||
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DISCHARGE
TUBE
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Discharge tube is a glass tube fitted with two electrodes placed opposite to each other. The tube is sealed and contains a vacuum pump. The function of vacuum pump is to reduced or change the pressure inside the tube. The two electrodes are connected to a high voltage battery. | ||||
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THE
EXPERIMENT
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| In discharge tube experiment, at low pressure and at very high potential difference, electric current is passed through the gas. | |||||
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OBSERVATION
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| Under different pressure different observations were noted; | |||||
At 1cm
Hg pressure: |
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| When pressure inside the tube is reduced to 1 cm of Hg, at a potential difference of a few thousand volts causes a spark to pass like a flash of light. | |||||
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At
1 mm Hg: |
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| At 1 mm Hg, the tube is mostly filled with a glow extending from the positive electrode. This is known as "positive column". | |||||
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At
0.001 mm Hg: |
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| At 0.001 m Hg, the glow disappears and the walls of the glass tube begin to glow with a brilliant green light. | |||||
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RESULT
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| These observations indicate that some radiation or rays are emitted from cathode. These rays are known as "Cathode Rays". | |||||
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PROPERTIES
OF CATHODE RAYS
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ORIGIN
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These rays originate from cathode. |
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PATH
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Cathode
rays travel in straight line. |
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PRESSURE
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Cathode
rays exert mechanical pressure. |
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SHADOW
FORMATION
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The cathode
rays consist of material particles because they produced shadow of objects
placed in the way. |
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EFFECT
OF ELECTRIC FIELD
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Cathode
rays deflect in applied electric field towards the positive terminal. |
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EFFECT
OF MAGNETIC FIELD
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Cathode
rays are deflected by magnetic field. |
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PENETRATION
POWER
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Cathode
rays penetrate small thickness of matter such as aluminum foil, gold foil,
etc. |
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CHARGE
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These rays
carry a negative charge. |
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DEPENDENCE
ON MATERIAL
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Cathode
rays are independent of the material of electrode or the nature of gas in
the tube. |
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e/m
RATIO
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Their
e/m ratio was equal to that of an electron. |
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CONCLUSION
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| Different
scientist tried different discharge tubes with different electrodes and
different gases but results of all the experiment gave same value for charge
to mass ratio. This shows that there is something common in all materials.
It was concluded that all the substances in common. Experiment shows that these particles could be produces from any kind of material. Cathode rays consist of particles which are known as electrons. |
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Contact
us:
info@citycollegiate.com |
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| For latest information , free computer courses and high impact notes visit : www.citycollegiate.com | |||||