Incandescent bulbs are designed by keeping in mind that the resistance of their filament increases with the
increase in temperature. If at room temperature, 100 W, 60 W and 40 W bulbs have filament resistances
R100, R60 and R40, respectively, the relation between these resistances is

• its my thought , according to hoops law, current is inverse of resistance , so we know all I = V/R
  here at room temperature means , current is constant (I=1).
  the relation between voltage and resistance is here differs, see V=IR
  here we have I value and v value and r value ,
  submit properly when the bulb is in 100W, the resistances also should be a same 100 only.
• 7 years agoHelpfull: Yes(0) No(0)