The above configuration shows three identical bulbs , Grade them in order of their brightness.

Explanation

`B_(1)&B_(2)` withdraw less current as compared to `B_(3)` because in series they give 2R resistance where as R is the reisitance dut to `B_(3)`.
Power `=i^(2)R`
`therefore` Brightness order : `B_(3)gtB_(2)=B_(1)`.