This video explains charge to mass ratio electron. J.J Thomson was able to measure the ratio of the electrical charge to the mass of the electron using a cathode ray discharge tube.
He applied electrical and magnetic field perpendicular to each other as well as to the path of the electrons.
when the magnetic field alone is turned on electron strikes the cathode ray tube at point C.
when electrical field alone is turned on ,the electron strikes at point A.
When both the magnetic and electric fields are off (or) when they are balanced, so as to cancel each other's effects, the electron strikes point B.
After doing these experiments, he was able to determine the value of charge to mass ratio as.
e / me = 1.758820.1011 c kg-1

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