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

Answer

D

Explanation

`R_(100) = (V^2)/(100), R_(60) = (V^2)/(60), R_(40) = (V^2)/(40)`
`(1)/(R_(100)) gt (1)/(R_60) gt 1/(R_40)`.