= electric potential
= change in potential energy (or simply )
Electron (proton) mass = 9.11×10−31kg (1.67× 10−27kg). Elementary charge = e = 1.602×10−19C.
=kinetic energy. 1 eV = 1.602×10−19J
near isolated point charge
Many charges: .
The alpha-particle is made up of two protons and two neutrons.
defines capacitance.
where A is area and d<<A1/2 is gap length of parallel plate capacitor
= stored energy
= energy density