Table 17-1. Comparison of quantities in gravity and electricity.Quantity Gravity Electricity
Uniform field
Field strength gDconst. EDconst.
Force FDmg FDqE
Potential GDgd VDEd
Potential energy UDmGDmgd UDqVDqEd
Point particles
Field strength gDGm=r^2 EDq=.4" 0 r^2 /
Force FDGm 1 m 2 =r^2 FDq 1 q 2 =.4" 0 r^2 /
Potential GDGm=r VDq=.4" 0 r/
Potential energy UDGm 1 m 2 =r UDq 1 q 2 =.4" 0 r/17.5 The Electron Volt
If a particle with an electric chargee(such as an electron or proton) is accelerated through a potential differ-
ence of 1 volt, it gains a kinetic energy of 1electron volt(eV). Note that the electron volt is a unit ofenergy,
not voltage. One electron volt is equal to1:6021766208 10 ^19 joules.
Notice that it doesn’t matter how far the charged particle travels, or how much time it takes to accelerate:
it only matters that the particle is accelerated through a potential difference of 1 volt. More generally, if a
chargeNeis accelerated through a potential differenceV, the particle will gain an energy ofNeVelectron
volts.
The electron volt is a common unit of energy in atomic and particle physics. Common multiples are the
kilo-electron volt (keV), mega-electron volt (MeV), and giga-electron volt (GeV).