Determination of Charge To Mass Ratio q and e
The charge to mass ratio e/m of an electron was determined by the scientist j.j Thomson
He used pear shaped apparatus which consist on screen evacuated glass tube two Aluminium Plates a Magnete Two Circular or Shaped Metallic Plotes a Cylinder and a Filament Connected With The Source
Working of Apparatus
When The Filament Was Heated a beam of Electron Was Produce This Beam of Electron was Accelerated By Appling The P. D of 1000v between the cylinder and circular plate A, in order to get a fine beam of electron further the P. d of 500v plates A and B when this fine beam of electrons passed through the inword magnetic field. It was defleated to word 'O' in place of "0" on the screen made of (zns) the circular path acquired by a beam of electron was due to the enistance of magnetic force which provides the centripetal force to this beam
Derivation Of Charge To Mass Ratio e/m
From The Given Figure it is clear That
It v, r and B are known Then (e/m) can be Determined easily.
Velocity Particle Selector Method
This Method is Use To Fined out the Velocity of beam of electrons in the pregence of electric Field and magnetic Field.
When j.j Thomson Connected the Aluminium plates With High Voltage Battery Then the Electric Field Was Produced. When Electric Force Balanced The Magnetic Force Then This Beam Of an Electron Was Moving in a Straight line without Any Deflection and Produced its Spot on "0" i.e at the Center Of Screen.
From the above Statement We Can Say That.
Other Expression For (e/m)
By Putting The Value Of v in Equation of (e/m) a New Expression For (e/m) Can be found.
.•.v= E/m
The Magnitude Of Charge on a Electron Was Determined by milicon which is equal to 1.602*10^-19 So We Can Say That.
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