Incandescent bulbs are designed by keeping in mind that the resistance of their…

PHYSICS · Single correct · CBSE · Physics · Current Electricity · Current Electricity

Problem

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

R_{100}

R_{60}

and

R_{40}

respectively, the relation between these resistances is [2010] (1)

\frac{1}{R_{100}} = \frac{1}{R_{40}} + \frac{1}{R_{60}}

(2)

R_{100} = R_{40} + R_{60}

(3)

R_{100} > R_{60} > R_{40}

(4)

\frac{1}{R_{100}} > \frac{1}{R_{60}} > \frac{1}{R_{40}}

Related theory

Electric Power
Temperature Dependence of Resistivity
Resistance & Resistivity
Electric Circuits
Electricity
Resistance: geometry and temperature dependence
Current Electricity

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