energy dissipation and efficiency

Question 1

energy can be either…?

Answer 1

useful or wasted

Question 2

what happens to wasted energy?

Answer 2

it is dissipated

Question 3

does friction dissipate energy?

Answer 3

yes, friction always caused energy to be transferred to a thermal store, which is then dissipated into the surroundings.

Question 4

what is the equation to find the total of the inputted energy?

Answer 4

input energy = useful output energy + wasted output energy

Question 5

what is the equation for efficiency?

Answer 5

efficiency = useful output / total input
(x100 if you want efficiency as a percentage)

Question 6

what is the equation for the useful output?

Answer 6

useful output = efficiency x total input

Question 7

what are sankey diagrams?

Answer 7

sankey diagrams are used to show the useful and wasted output of the total input energy

Question 8

what does the top arrow on a sankey diagram represent?

Answer 8

the useful output (measured in joules)

Question 9

what does the bottom arrow on a sankey diagram represent?

Answer 9

the wasted output (measured in joules)

Question 10

what does the total width of the left side on a sankey diagram represent?

Answer 10

the total energy input (measured in joules)

Question 11

how do you reduce the energy wasted by friction?

Answer 11

use an oil to lubricate the moving parts to reduce friction

Question 12

how do you reduce the energy wasted from resistance in a wire?

Answer 12

use a wire with a larger cross-sectional area, and made with a less resistive material

Question 13

how do you reduce the energy wasted by air resistance?

Answer 13

make the object more aerodynamic

Question 14

how do you reduce the energy wasted through sound created by machinery?

Answer 14

tighten loose parts in the machine to reduce unnecessary movement