Energy Flashcards
(18 cards)
Gravitational potential energy eq
Mass x gravitational field strength x height
GPE = mgh
Kinetic energy eq
1/2 x mass x velocity^2
KE = 1/2 x m x v^2
Efficiency
Useful / total input (x 100 for %)
e = et / eu
Dissipating energy
The irreversible process where energy is transformed (spread to its surroundings) - usually to heat. The final form has less capacity than the initial form
Conservation of energy
Total energy remains the spasme before and after a change
E.g. max GPE (at highest point) = max KE (at lowest point)
How do mechanical processes cause wasteful energy to be dissipated
High currents give more kinetic energy to cause more collisions, meaning more heat is lost and efficiency is lower
Step up transformers
Increases the voltage which decreases the current so efficiency increases
Step down transformers
Decreases the voltage, increases the current and decreases the efficiency
Ways of reducing unwanted energy transfers
Lubrication and thermal insulation
Lubrication
Reduces friction which, not only reduces heat loss, but also reduces wear and tear on moving parts. Used for machines in industry
Thermal insulation
Using a material with a low thermal conductivity insulates and keeps areas hot. Used in buildings
Why is heat loss a negative
It costs money, needs fuel which is not sustainable
Non-renewable
An energy source that takes a long time to be formed so it will eventually run out
Non-renewable resources
Fossil fuels (oil, natural gas, coal), nuclear fuel (uranium and plutonium)
Disadvantages of non-renewable resources
Run out one day, release greenhouse gases such as CO2 (coal the most) which contributes to global warming, coal and oil release sulfur dioxide which causes acid rain, nuclear is difficult to dispose and is radioactive, pollution
Higher thermal conductivity
Loses more heat and cools quicker. Needs low thermal conductivity and thick walls
Patterns and trends of energy resources
Renewable has increase as it is more sustainable and contributes less to or doesn’t contribute at all to global warming
Power def
The rate at which energy is transferred
