I want to know the answer to the following question:
How does filament size relate to voltage level?
All the background I'm provided with is that "A lamp with the same rated lifetime but designed for 230 V would produce only around 12.8 lumens per watt, and a similar lamp designed for 30 volts (train lighting) would produce as much as 19.8 lumens per watt.". Is that enough to answer the question?