corona takes place at a voltage, lower than breakdown voltage

corona takes place at a voltage higher than breakdown voltage

corona is a current phenomenon

corona increases the transmission line efficiency

Non sinusoidal

Sinusoidal

D.C.

Square

the distance between the conductors is reduced

the conductor diameter is reduced

bundled conductors are used

stranded conductors are used

the current density is reduced

the eddy current in the conductor is eliminated

for a given cross section, the radius of the conductor is increased

of better ventilation in the conductor

diameter of the conductor

material of the conductor

height of the conductor

none of above