filament lamp:
cost-80p
efficiency-0.2
expected life- 1000 hours
compact fluorescent lamp (CFL):
cost- £3.00
efficiency-0.8
expected life- 8000 hours
A filament lamp with a power rating of 100 w gives 2000 units of light. what power rating would a CFL need to provide 2000 units of light?
1) 8000 W
2) 20 W
3) 25 W
4) 25 kW