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Acceleration of electrons

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umair khan

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when we apply a voltage to a any material like semi conductor an eletric field is produced to drift the electrons. it is a force F=-qE so according to newton's law
F=ma
, the electrons should be accelerated but why they don't
 

You must keep in your mind the crystallographic structure.Since electron in motion will collide with different atoms ,thus that electron will face an opposing force.At steady state the applied force will be equal to opposing force.Thus it will move with constant velocity
 

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    umair khan

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I think that the electrons are accelerated until they reach a saturation velocity ,and increasing the electric field further doesn't accelerate electrons any more due to scattering effects(I am not sure).
 

MSSN said:
I think that the electrons are accelerated until they reach a saturation velocity ,and increasing the electric field further doesn't accelerate electrons any more due to scattering effects(I am not sure).
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yes of course ..electrons cannot be accelerated fiurther..it is only upto saturation velocity.....
 

If the electrons are travelling at saturation velocity ,whatever the voltage is applied then there will be a fixed number of charges coming out of the material at a given time.Fixed number of electrons means fixed charge per unit time, which means constant current independent of voltage which is not the case .

Thus i think saturation velocity is just an upper limit ,when voltage applied is exceeded the electrons can not exceed the saturation velocity.For normal cases electrons will moving at speed which is dependent on voltage applied
 

Hi
This applies perfectly in vaccum and for single electron because if not you have to put into consideration collision with other particles and forces between electrons.
 

electrons have a valence charge move them out of horbit you have caused an empty space available that space will be repaced by a new electron. so electrons go one way holes go the other way. the speed is constant vacum or not like the speed of light constant 300mega over lambda i beleive i forget.\][/list][/code]
 

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