But if power is directly proportional to resistance in case of series, why is it that the power isn't highest in the bulb with maximum resistance because power should increase with resistance? Has this got anything to do temperature?
Also when bulb is connected in the circuit, the resistance of the bulb increases as the time for which current passing through the circuit increases. As the current passes through the circuit, the circuit gets heated up and increases the temperature of the filament. This increase in temperature of the filament in the bulb is responsible for the increase in resistance of the bulb. Hence we conclude that there is a relationship between resistance of the bulb and its temperature.