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

Options

A. `(1)/(R_(100)) = (1)/(R_(40)) + (1)/(R_(60))`
B. `R_(100) = R_(40) +R_(60)`
C. `R_(100) gt R_(60)gt R_(40)`
D. `(1)/(R_(100)) gt (1)/(R_(60)) gt (1)/(R_(40))`

Answer

d

Explanation

As `P prop (1)/(R) or R prop (1)/(R)`
so `(1)/(R_(100)) gt (1)/(R_(60)) gt (1)/(R_(40))`