PC is only running on 12 volts although the monitor is probably 240v but usually much smaller screen than most TVs, I'm sure someone will give you more precise figures than me though.
A computer is just like a TV, except it also has mechanical components (hard disks, etc).
A TV is just like a computer monitor without the computer.
Logically, therefore (and assuming that the computer has sound) a computer uses more power than a TV.
Incidentally, RATTER15, the voltage is irrelevant. A car starter motor runs on 12 Volts and (according Toyota's specs fro their 4 cylinder models) consumes around 1,680 watts.