How Do You Calculate the Filament Area Ratio Between Main and Car Head Lamps?

[marco123]

hi all i have a question to do but i can't seem to get my head round it and i was hoping some of you might be able to explain it better so here it is:
"the coiled filaments in a main lamp and a car head lamp are made of the same material and have the same length. Use the info. below to calculate the ratio:
cross sectional area of the mains lamp filament/cross sectional area of the headlamp filament

Mains lamp: 230V; 100W Car headlamp;12V; 36W

Many thanks
Marco

 

[LowlyPion]

hi all i have a question to do but i can't seem to get my head round it and i was hoping some of you might be able to explain it better so here it is:
"the coiled filaments in a main lamp and a car head lamp are made of the same material and have the same length. Use the info. below to calculate the ratio:
cross sectional area of the mains lamp filament/cross sectional area of the headlamp filament

Mains lamp: 230V; 100W Car headlamp;12V; 36W

Many thanks
Marco

Your power is W = I²R

What do you suppose are the differences in current between the 2?