What is skin effect and methods to reduce skin effect?

Answer 1

with the inductance of a conductor it tends to push current flow to the outside

to reduce the effect you make the conductor hollow

with 80 hz and Cu conductor the current is in the outer 8mm or so.

Answer

You cannot really reduce the skin effect in ordinary conductors; for the sake of economy, you can use tubular conductors. Tubular conductors do not reduce the skin effect, but merely saves copper (if little current flows towards the centre, why have a centre!). However, special, insulated, conductors ('litz' wire) woven or braided in various patterns, can be used for special applications (e.g. high-frequency transformer windings) up to around 1 MHz or so. Because each strand has a very small cross-sectional area, and is insulated from its adjacent conductors, the skin effect is negligible compared with if it were a solid conductor.