If an electron is accelerated by a potential difference of 2.5 V it would gain energy of . (Take charge of electron 1 × 10⁻¹⁹C)

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(3) 2.5 eV. Idea: a charge q moved through a potential difference Δ V gains energy W=q Δ V. For an electron q=e, so W=e×2.5 V. One electron volt is defined as the energy gained by charge e through 1 V, so W=2.5 eV — the size of e is not needed to name the answer in these units. In joules, with the value printed in the paper: W=1×10⁻¹⁹×2.5 = 2.5×10⁻¹⁹ J; with the accepted e=1.6×10⁻¹⁹ C it would be 4×10⁻¹⁹ J. Either way the energy in electron volts is 2.5 eV, because the volt-to-electronvolt step cancels whatever value of e is used.

If an electron is accelerated by a potential difference of 2.5 V it would gain energy of ________. (Take charge of electron 1 × 10⁻¹⁹C)

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