1A)
A filament lamp-
cost- 80p
effiency- 0.2
expected life- 1000 hours
a compact fluorescent lamp (CFL)-
cost- £3.00
effiency- 0.8
expected life- 8000 hours
a filament lamp with a power rating of 100W gives 2000 units of light.
what power rating would a CFL need to provide 2000 units of light?
a)8000W
b)20W
c)25W
d025W
1B)
elecricity costs 15p per KWh.
what will be the cost of using a 100W filament lamp during it's expected life?
a)£1.50
b)£15.00
c)£150.00
d)£1500.00
1C)
in it's lifetime, a security light is used for 15000 hours.
how much would you expect to spend on buying CFLs for the security light in that time?
a)£5.63
b)6.00
c)12.00
d)£45.00
1A) To answer this question, we need to calculate the power rating of a CFL that would provide 2000 units of light. The efficiency of the filament lamp is given as 0.2, while the efficiency of the CFL is given as 0.8.
First, we calculate the power rating of the filament lamp using the formula:
Power rating = Units of light / Efficiency
Power rating = 2000 / 0.2
Power rating = 10000W
Next, we can use the efficiency of the CFL to calculate its power rating using the same formula:
Power rating = Units of light / Efficiency
Power rating = 2000 / 0.8
Power rating = 2500W
Therefore, the power rating a CFL would need to provide 2000 units of light is 2500W. None of the options provided (8000W, 20W, 25W, 0.25W) matches the correct answer.
1B) To calculate the cost of using a 100W filament lamp during its expected life, we need to calculate the energy consumed in kilowatt-hours (KWh) and then multiply it by the cost per KWh.
First, calculate the energy consumed in KWh using the formula:
Energy consumed = Power rating (in kilowatts) × Time (in hours)
Energy consumed = 100W / 1000 (to convert to kilowatts) × 1000 hours
Energy consumed = 100 KWh
Next, calculate the cost of energy consumed by multiplying the energy consumed by the cost per KWh:
Cost = Energy consumed × Cost per KWh
Cost = 100 KWh × £0.15/KWh
Cost = £15
Therefore, the cost of using a 100W filament lamp during its expected life is £15.00 (option b).
1C) To calculate the amount spent on buying CFLs for the security light over its lifetime, we need to calculate the number of CFLs required and then multiply it by the cost of each CFL.
First, calculate the number of CFLs required using the formula:
Number of CFLs = Total time / Expected life of a CFL
Number of CFLs = 15000 hours / 8000 hours
Number of CFLs ≈ 1.875
Since we cannot buy a fraction of a CFL, round up to 2 CFLs.
Next, calculate the cost of buying 2 CFLs by multiplying the number of CFLs by the cost of each CFL:
Cost = Number of CFLs × Cost per CFL
Cost = 2 × £3.00
Cost = £6.00
Therefore, the amount expected to be spent on buying CFLs for the security light in that time is £6.00 (option b).