Conductivity

• The (electrical) resistivity (or specific resistance (התנגדות סגולית)) $\rho$ (in $\mathrm{\Omega }\cdot \mathrm{m}$) of a material is a measure of how strongly that material opposes the flow of electric current
  • $\rho =\frac{E}{J}$ where $E$ is the electric field (in $V/m$) and $J$ is the current density (in $A/{\mathrm{m}}^2$)
  • $\rho (T)={\rho }_0[1+\alpha (T-T_0)]$
• The reciprocal of the resistivity, called the electrical conductivity (or specific conductance (מוליכות סגולית)) is $\sigma =\frac{1}{\rho }$ (in $S/m$, siemens per meter, or $(\mathrm{\Omega }\cdot \mathrm{m}{)}^{-1}$)
  • factors:
    • metals and ionic compound are good conductors, while molecular compound are poor ones
    • strong electrolytes → high conductivity, weak electrolytes → low conductivity
    • temperature