How does a large electric switch different from small?
Larger switches allow the contacts to be further separated when switching off. If you switch a large current off the contacts will draw an arc that will burn the contacts. In AC that's not as bad as in DC, because the zero-crossing will extinguish the arc. But in DC the arc can persist for longer time, and will only extinguish by pulling the contacts far enough apart.  

High voltage switches (110V/230V) are larger because they need a better isolation between the voltage at the contacts and the user operated lever.