Search results
Results from the WOW.Com Content Network
Continuous charge distribution. The volume charge density ρ is the amount of charge per unit volume (cube), surface charge density σ is amount per unit surface area (circle) with outward unit normal n̂, d is the dipole moment between two point charges, the volume density of these is the polarization density P.
The upper graph shows the current density as function of the overpotential η . The anodic and cathodic current densities are shown as j a and j c, respectively for α=α a =α c =0.5 and j 0 =1mAcm −2 (close to values for platinum and palladium).
Linear charge density (λ) is the quantity of charge per unit length, measured in coulombs per meter (C⋅m −1), at any point on a line charge distribution. Charge density can be either positive or negative, since electric charge can be either positive or negative. Like mass density, charge density can vary with
The equations introduce the electric field, E, a vector field, and the magnetic field, B, a pseudovector field, each generally having a time and location dependence. The sources are the total electric charge density (total charge per unit volume), ρ, and; the total electric current density (total current per unit area), J.
When charged particles move in electric and magnetic fields the following two laws apply: Lorentz force law: = (+),; Newton's second law of motion: = =; where F is the force applied to the ion, m is the mass of the particle, a is the acceleration, Q is the electric charge, E is the electric field, and v × B is the cross product of the ion's velocity and the magnetic flux density.
ρ is the free electric charge density (in units of C/m 3) J is the current density J = ρ v {\displaystyle \mathbf {J} =\rho \mathbf {v} } with v as the velocity of the charges. The equation would apply equally to masses (or other conserved quantities), where the word mass is substituted for the words electric charge above.
As such, the fine-structure constant is chiefly a quantity determining (or determined by) the elementary charge: e = √ 4πα ≈ 0.302 822 12 in terms of such a natural unit of charge. In the system of atomic units , which sets e = m e = ħ = 4 πε 0 = 1 , the expression for the fine-structure constant becomes α = 1 c . {\displaystyle ...
mass density usually simply called density kilogram per cubic meter (kg/m 3) volume charge density: coulomb per cubic meter (C/m 3) resistivity: ohm meter (Ω⋅m) sigma: summation operator area charge density: coulomb per square meter (C/m 2) electrical conductivity: siemens per meter (S/m) normal stress: pascal (Pa)