- #1
erisedk
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Homework Statement
Incandescent bulbs are designed by keeping in mind that the resistance of their filament increases with an 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:
(A) ## \dfrac{1}{R_{100}} = \dfrac{1}{R_{40}} + \dfrac{1}{R_{60}} ##
(B) ## R_{100} = R_{40} + R_{60} ##
(C) ## R_{100} > R_{60} > R_{40} ##
(D) ## \dfrac{1}{R_{100}} > \dfrac{1}{R_{60}} > \dfrac{1}{R_{40}} ##
Homework Equations
P = ##I^2R##
P = ##\frac{V^2}{R}##
The Attempt at a Solution
I am extremely confused on this one. I think if we connected them all in series, which would mean that the current flowing through all three bulbs is the same, the resistance of each of them would increase, so power would increase but then this would decrease the current, so the power would still be the same etc. Then I tried similar things with fixed voltages, but I keep going around in circles, so if anyone could give me a starting point?
Thank you.