When accelerated from rest, the energy is fully kinetic. So, KE = charge × potential difference, i.e.
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MV2=Q.V, From the given equation, it is obvious that velocity of particle is inversely proportional to the mass of particle. So, an electron will gain more speed as it has a lower mass than that of a proton. Also, as the energy is fully kinetic, an electron will have greater energy as a result of greater velocity.