Two dissimilar bulbs are connected in series. Which bulb will be brighter?
(Hint: Consider the resistance of each bulb.)

Explanation

The bulb of higher resistance will be brighter, assuming that the filaments of the two bulbs have the same length and the same area of cross section, but are made of metals with different resistivities.
[Explanation : Heat produced (H) in time `t =I^(2)Rt` , where I is the current through a conductor and R is the resistance of the conductor. In a series combination, the current through each conductor is the same. `therefore H prop R` for a given t. Hence, the bulb with higher R will become more hot and hence emit more light energy per second. Here it is assumed that the filaments of the two bulbs have the same length and the same area of cross section, but are made of metals with different resistivities. ]