The values of charge (e) and mass ( m ) of the electron always remain the same whatever may be the source of their emission. In the discharge tube, the electrons may be emitted either from the cathode or from the gas enclosed in the discharge tube. Whatever may be the metal which forms cathode or the gas present in the discharge tube, these values remain the same. Therefore, electron is regarded as a universal particle.
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The electron is an elementary particle. It cannot be further divided into more divisions. Also other particles are through to have condensed from combinations of these. Thus electron is called a universal particle.