Electrical Energy Flashcards
1
Q
what is the main power equation for electricity
A
P=IV
2
Q
what would you do to that equation to work out the energy transferred
A
multiply by t
3
Q
what does multiplying by t do to the equation
A
- Pt = IVt
- as P =W / t, W = Pt
- so W = IVt
- and work done = energy transferred
- so E = ItV
4
Q
how does a filament lamp simply radiate light
A
- the current heats up the filament in the lamp
- by converting its electrical energy to thermal energy
- and by raising the temperature of the filament it radiates electromagnetic radiation
5
Q
why might a filament lamp be an inefficient way of generating light
A
- because only 10% of the electromagnetic radiation produced is in the visible spectrum
- the rest of the energy is mainly in the infrared part of the spectrum
6
Q
what does low energy CFL and LED stand for
A
- compact fluorescent lamps
- light emitting diodes
7
Q
what is a disadvantage of using CFLs over filament lamps
A
- they cost more to manufacture
- so are more expensive
8
Q
what is the main advantage that comes with using CFLs
A
- they produce the same amount of light for nearly 25% less of the energy a filament lamp would use
- and they last about 8 times longer (8000 hours)
9
Q
what would the impact be of replacing a filament lamp with a CFL be environmentally
A
- it would reduce emissions of CO2 by 40kg a year
- if each house in the uk installed 3 low energy lamps, it would save enough energy to run the countrys street lights for a year
10
Q
how do the light outputs and energy consumption of an LED and halogen light compare
A
- a 4W LED lamp would give an equivalent light output
- to a 50W halogen lamp
