General questions (not homework)

Hello Friends

Q.1 In General current in 1kva single phase transformer ?

Q.2 if 2 conductor 1 placed in 20c temperature and
other one placed in 100c temperature and then bring it in 20c (this process repeated about 100 times) then both conductors placed in 20c temperature and flow current in them so which give higher resistance.to current?

Q.3 which take more energy(Mechanical)to produced 160v 60hz or 220-240 50hz

thanks questions