Accepted Answer
If 50 identical light bulbs are connected in series across a single power source, then the voltage across each bulb is ( 1/50 ) of the voltage delivered by the power source.
Suggested Answer
Presuming that this tree is connected into a mains power source in the UK. The total output of the UK mains source is 230V. So if we share this voltage equally between 50 bulbs:[tex]230V \div 50 = 4.6V[/tex]I'm not 100 per cent sure this is correct though and different countries may have different mains power supplies. Hope it helps anyway.EDIT: This also does not take into account resistance in the bulbs and wires but is all I can tell you from the information provided in the question.