Why shouldnt an bulb and a heater connected in series ?
As you know that, In a series circuit the current is constant throughout the electric circuit. Thus it is obviously impracticable to connect an electric bulb and an electric heater in series, because they need currents of widely different values to operate properly. Another major disadvantage of a series circuit is that when one component fails the circuit is broken and none of the components works.
In series current remain same and voltage divided according to the resistance of the appliecne. Now when you put electric bulb and heater in series then it will divide the voltage which ultimately divided the power double asP (power) = V2/Rwehre V is voltage and R is resistanceif V reduce one fold power will reduce 2 fold