Bulb B1(40W, 220V) connected to a 220V supply glows with some brightness. Predict the change in brightness(if any) with reason if another identical bulb B2(40W, 220V) is connected in:-

(a) Series to B1
(b) Parallel to B1

(a) In series, resistance of the circuit increases , hence current in the circuit decreases so power across the bulb b1 decreases, so brightness decreases.
(b) In parallel, resistance of the circuit decreases, hence current increases so power increases, so brightness increases.