Energy and efficiency Flashcards
1
Q
How is work calculated?
A
W (J) = F (N) x s (m)
2
Q
How is percentage efficiency calculated?
A
(useful energy output/ energy input) x 100%
3
Q
The power input to a computer is 120W, and the computer wastes 40J over 10 seconds through heat and sound. Calculate the percentage efficiency of the computer.
A
P= ∆E / ∆t, = 40 / 10 = 4W wasted. Useful output= 120-4 = 116W. Efficiency = (116/120) x 100% = 96.7%.
