Conservation of Energy Flashcards
What is the principle of energy conservation?
Energy can neither be created or destroyed, only transferred, stored and dissipated
Total energy input = useful energy output + waster energy
What are the three categories of energy transfers and what decides the two types of output energies?
Input, output and waste. The empirical experience of the characteristics decides if it is either waste or useful ( if it is required for the purpose).
What is the diagram that shows energy transfers and what is important about the width of the arrows?
A Sankey diagram.
Both arrows must equal the width of the total energy imputed.
What is the equation for efficacy?
Efficacy = useful output energy divided by total input energy x 100 %
What does it mean if a filament light bulb is less efficient than an energy saving lightbulb?
It means that the total percentage of useful energy in a filament lightbulb is smaller than in an energy efficient one.
What is the equation of kinetic energy?
Kinetic energy = 1/2 x mass x velocity squared
Mass(kg) velocity (m/s)
What is the equation for gravitational potential energy?
Gravitational potential energy = gravitational field strength x mass x height ( GPE = G x M x H )
Or
Gravitational potential energy = weight x height ( GPE = W x H)
What are the energy resources( ways if generating energy )?
Hydro electrical, geothermal, fossil fuels, wind, solar, waves, biomass, nuclear, tidal.
What are the advantages and disadvantages renewable energy resources?
Renewable disadvantages: unreliable Expensive for original purchase Place dependent Engineers have to take into consideration bird migration routes. Renewable advantages : Relatively cheap to run once bought Eco- friendly Can be reliable e.g. tidal
What are the disadvantage and advantages of non- renewable energy resources?
Non-renewable Advantages : Affordable Cheap Easy to transport Reliable Non-renewable disadvantages: Bad for the environment Slowly running out - Consumption is quicker then manufacture Dangerous to dispose of
How has the use of energy differed over time and why?
The use if energy has differed over time as we are slowly beginning to run out of fossil fuels due to the high levels of consumption over the past years. We are experiencing the drawbacks of non-renewable energy now such as climate change and global warming so the desire to convert to renewable energy is beginning.
What is kinetic and thermal energy?
Kinetic - anything moving has energy in its kinetic energy store (mass and speed determines how much)e.g. the great the mass the more energy so faster it travels
Thermal(heat) - any object (the hotter it is the more energy it has)
What is chemical and gravitational potential energy?
Chemical -anything that can release energy by a chemical reaction
Gravitational potential - anything in a gravitational field strength (anything that can fall)
What is elastic potential and electrostatic energy?
Elastic potential - anything stretched such as springs or bands
electrostatic - to charges that attract or repel each other
What are magnetic and nuclear energy stores?
Magnetic - two magnets that attract or repel each other
Nuclear - atomic nuclei release energy from this store in nuclear radiation
What is the equation for kinetic energy?
Kinetic energy = 0.5 x mass x velocity2
What is the equation for gravitational potential energy?
Change in GPE = mass x gravitational field strength x change in vertical height
How can energy be mechanically transferred?
-Mechanically - a force acting on an object like push
When is energy useful?
When it is transferred from one store to a useful store
Some energy is usually dissipated as heat to the surroundings
What is lubrication?
Lubrication reduces energy transferred by friction (usually when something is moving
How does lubrication work?
It reduced friction by lubricating object surfaces with liquids such as oil so they can flow easier.
This reduced heat loss but also reduces wear and tear so is often used in machines
What is insulation?
Reduced the rate of energy transfer by heating
How does insulation work?
- In a building, the lower the thermal conductivity of its walls the slowed the rate if energy transfer through them (cool slower) so insulates buildings (or you can make walls thicker)
- Cavity walls with an air gap between inner and outer walls reduces energy transferred by conduction as air has low thermal conductivity
What is biofuel, the advantages and disadvantages?
- they are created from plants and waste and can be burnt to produce electricity by heating water, steam turns turbine
- they are fairly reliable, quick to produce, are continually produced and stored as otherwise they cannot respond to immediate demands
- the cost to refine bio-fuel is very high, areas of forest may be cleared to make room to grow them -loss of habitats and decayed vegetation increases methane and carbon dioxide
What is wind power, the advantages and disadvantages?
- each wind turbine has an internal generator which turns the blades to turn the generator and produce electricity
- initial costs are quite high, lots are needed to produce a sustainable amount of power, they can spoil views, noisy, wind dependent
- no damage to the environment, cost is minimal to run
What are solar cells, advantages and disadvantages?
- solar cells use energy transferred by light to create an electrical current
- no pollution, running costs are minimal
- day dependent, not sustainable for countries that aren’t sunny, initially expensive, relatively small scale
What is hydroelectricity, advantages and disadvantages?
- usually involves flooding a valley by building a dam. This means rainwater is caught and allowed out through turbines
- no pollution, reliable all year round so constant source, can immediately respond to increase demand as more water can be let out by turbines, minimal running costs
- initially expensive, flooding can cause loss of habitat, decaying vegetation under the water can produce greenhouse gases
What are tidal barrages, advantages and disadvantages?
- big dams built across rover estuaries with turbines in them so when the tide comes, estuary is filled and let out through turbines
- no pollution, pretty reliable, minimal running cost and no fuel cost
- initial cost relatively high, alter habitats, spoil views, affect boat access
What may limit the use of renewable energy?
- these new power plants are very expensive
- arguments over where they should be, not near housing in some cases
- less reliable than fossil fuels to meet the demand
- personally, not everyone can afford these changes (e.g. hybrid cars)
How can energy be transferred by heating?
By heating - energy transferred from a hot object to a colder one
How can energy be transferred by radiation?
by radiation - energy transferred by waves
How can energy be transferred electrically?
-Electrically - a charge doing work against resistance like in a circuit
What happens when energy is transferred to a ball rolling up a slope?
The ball does work against the gravitational force, so energy is transferred mechanically from the kinetic energy of the to ball to its gravitational potential energy
What is the energy transferred from a bat hitting a ball?
- bat has kinetic energy in its store and some if this is transferred mechanically to the ball’s kinetic energy store
- some also transferred mechanically to thermal energy stores
- rest is carried away by sound
What is the energy transferred by a rock dropped from a cliff?
- assuming no air resistance, gravity doesn’t work on the rock so it co say toy accelerates towards the ground
- energy transferred mechanically from GPE store to KE store
What happens to the energy transfer of a car slowing down?
-cars kinetic energy store is mechanically and then by heating to the thermal energy stores of the car and the road due to friction
What happens to the energy transfer of the kettle boiling water?
-energy transferred electrically from the mains to the heating element of the kettle and then by heating to the thermal energy store of the water
What energy transfers happen for a girl on a swing?
- originally pushed she has maximum amount of GOPE as she is at her highest point
- as she swings downwards she looses GPE as he height decreases but gains KE due to the forces (weight) acting on her
- as swing rises she looses KE due to a gain in GPE
- throughout swing the back and forth motion gradually decreases in height as some energy dissipates to the surrounds as heat energy due to opposing forces like air resistance
Principal throughout the spring?
Total GPE and KE is constant so loss in GPE equals a gain in KE
