Resistance and Resistors

Ohm's Law states that current is proportional to voltage; circuits are ohmic if they obey the relation V=IR.

Superconductivity is a phenomenon of zero electrical resistance and expulsion of magnetic fields in certain materials below a critical temp.

Resistance and resistivity describe the extent to which an object or material impedes the flow of electric current.

Resistivity and resistance depend on temperature with the dependence being linear for small temperature changes and nonlinear for large.