Electron Charge to Mass Ratio


What is the significant of the charge to mass ratio? Will we get the same value of 1.76 x 10 *11 C kg*-1 if the charges used is not an electron? Why should we always use electrons in the experiment?

It is said in our textbook that the trajectory of electron beam is independent on the charge and mass of the particle used. But why not if the charge increases, the electric force on it increases and thus curves more?


Knowing the charge to mass ratio allows us to calculate the mass by measuring charge effects. Among other things this provided confirmation of the special theory of relativity. The charge to mass ratio in the context you find it refers only to the electron. Each charged particle has its own charge to mass ratio. We use electrons in many experiments because they are conveniently provided by thermionic emission. Other charged particles are more difficult to produce and capture.

According to Newton's second law the acceleration of a particle is the force divided by the mass. Since the force on a charged particle is proportional to its charge, the deflection of a beam of charged particles will be the same for all particles with the same charge to mass ratio. So the deflection is independent of the charge and the mass only as long as the ratio of charge to mass is maintained.