Dielectric strength: The maximum value of electric field (on potential gradient) that a dielectric material can tolerate without it's electric break down and it's dielectric strength.
S.I. unit of dielectric strength of a material is v/m but practical unit is mv/mm.
Relative permeability: It is the degree or extent to which magnetic lines of force ca enter a substance and is denoted by μ.e.g., permeability of soft iron is 1000 time greater than that of air.
