![]() ![]() ![]() For example, about 5 eV of energy is required to break up certain organic molecules. The electron-volt is commonly employed in submicroscopic processes-chemical valence energies and molecular and nuclear binding energies are among the quantities often expressed in electron-volts. These simple relationships between accelerating voltage and particle charges make the electron-volt a simple and convenient energy unit in such circumstances. Similarly, an ion with a double positive charge accelerated through 100 V gains 200 eV of energy. ![]() A potential difference of 100,000 V (100 kV) gives an electron an energy of 100,000 eV (100 keV), and so on. It follows that an electron accelerated through 50 V gains 50 eV. Īn electron accelerated through a potential difference of 1 V is given an energy of 1 eV. (Note that in terms of energy, “downhill” for the electron is “uphill” for a positive charge.) Since energy is related to voltage by Δ U = q Δ V Δ U = q Δ V, we can think of the joule as a coulomb-volt.ġ eV = ( 1.60 × 10 −19 C ) ( 1 V ) = ( 1.60 × 10 −19 C ) ( 1 J/C ) = 1.60 × 10 −19 J. The electron gains kinetic energy that is later converted into another form-light in the television tube, for example. An electron is accelerated between two charged metal plates, as it might be in an old-model television tube or oscilloscope. It is useful to have an energy unit related to submicroscopic effects.įigure 7.13 shows a situation related to the definition of such an energy unit. The particle may do its damage by direct collision, or it may create harmful X-rays, which can also inflict damage. For example, even a tiny fraction of a joule can be great enough for these particles to destroy organic molecules and harm living tissue. But on a submicroscopic scale, such energy per particle (electron, proton, or ion) can be of great importance. The energy per electron is very small in macroscopic situations like that in the previous example-a tiny fraction of a joule. How many electrons would go through a 24.0-W lamp each second from a 12-volt car battery? The Electron-Volt To have a physical quantity that is independent of test charge, we define electric potential V (or simply potential, since electric is understood) to be the potential energy per unit charge: But we do know that because F → = q E → F → = q E →, the work, and hence Δ U, Δ U, is proportional to the test charge q.
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