Help with the ARC option

Could someone please help me to figure out how I would make what you would see on an oven control knob where you turn it from high to low... and you know how some oven control knobs has the solid line that begins small at low temp and then the line gradually widens when its at the high/hot temp.?....?     Well,  I see where I can do the ARC and that is exaclty what I want it to look like.  But I dont know how to get that ARC line to start off small and gradually thickens at the other end.  help