is more directive

is less directive

is the same

exhibits no directivity at all

$${{j\omega \mu } \over \sigma }$$

$${{j\omega \in } \over \mu }$$

$$\sqrt {{{j\omega \mu } \over {\sigma + j\omega \in }}} $$

$$\sqrt {{\mu \over \in }} $$

conductor always.

conductor or dielectric depending on the applied electric field strength.

conductor or dielectric depending on the frequency.

conductor or dielectric depending on the electric current density.

is proportional to the electric field for all values of electric field

is independent of the electric field

increases at low values of electric field and decreases at high values of electric field exhibiting negative differential resistance.

increases linearly with electric field at low values of electric field and gradually saturates at higher values of electric field.