Energy Part 2 Flashcards
Types of energy stores
- chemical energy: stored in fuel, food, batteries
- kinetic energy: in moving objects
- gpe: in objects raised above the ground
- epe: in stretched or compressed objects like springs
- thermal energy : in objects ata a certain temperature
- magnetic energy: in magnets and magnetic fields
- electrostatic energy: in charged particles
- nuclear energy: in atomic nuclei
What is a system
- an object or group of objects
- energy is transferred into or out of the system
Example of energy systems
- a kettle transfers electrical energy to thermal energy of the water
- a person lifting a weight transfers chemical energy from food to gravitational potential energy
Mechanisms of a transfer
- mechanically: by a force moving n object
- electrically: when charges move through a potential difference
- heating: energy transferred from hotter to cooler objects
- radiation: energy transferred by waves, e/g/ light or sound
Conservation of energy
Energy cannot be created or destroyed, only transferred, stored or dissipated
Dissipation
When energy spreads out and becomes less useful (usually as heat)
What is specific heat capacity
- the amount of energy needed to raise the temperature of 1 kg of a substance by 1 degree Celsius
Thermal insulation
- cavity walls (air gap reduces conduction)
- loft insulation (reduces convection)
- double glazing (traps air, reduces conduction)
- carpets and curtains (reduce heat loss)
Renewable resources
- wind - turbines turned by wind
- solar - solar panels convert sunlight to electricity
- hydroelectric - falling water turns turbines
- tidal - tides turned by wind turbines
- wave - sea waves turn turbines
- geothermal - heat from underground
Pros and cons of renewable resources
Pros:
- wont run out of
- low pollution
Cons:
- weather dependent
- some can affect wildlife or land use
Non-renewable resources
- fossil fuels: coal, oil, gas
- nuclear: uranium and plutonium
Pros and cons of non renewable resources
Pros:
- reliable
- high energy output
Cons:
- produce greenhouse (except nuclear)
- limited supply
- environmental damage
Type of energy resources
- transport: petrol/diesel (non renewable), electric vehicles (renewable if electricity is from renewables)
- heating: gas, oil, coal (non renewable); solar water heaters, heat pumps
- electricity: from any source
Trends in energy resource use
- past: heavy reliance on fossil duels
- now: more use of renewables due to:
-environmental concerns
-technology improvements
-political and social pressure - issues:
-cost of switching
-reliability
-limited capacity of some renewables
Elastcially deformed
when and object goes back to its original shape after the force is removed
What is inelastically deformed
When an object doesn’t return to its original shape
Hooks law
- extension is directly proportional to the force as long as you’re within the springs limit of proportionality
What is spring constant
- measures how stiff a spring is
- a larger ‘k’ means a stiffer spring - it takes more force to stretch
Required practical of investigating springs
- Hang a spring from a clamp
- Add masses, 100g at a time, and measure the extension using a ruler
- Plot a graph of force vs extension
Conclusion of experiment
- graph should be a straight line at first
- eventually the lie curves - spring has passed its elastic limit
Specific heat capacity
- Measure the mass of the block using a balance
- Insert the heater add thermometer into the holes
- Wrap the block in insulation to reduce energy loss
- Switch on the heater and record:
- time (s)
- initial and final temperature
- energy supplied - Use the equation to calculate specific heat capacity
- use a lif or more insulation to reduce heat loss
What is efficiency
Efficiency tells us how much of the input energy is usually transferred
How to improve efficiency
- lubrication to reduce heat loss by friction
- thermal insulation reduces heat loss
- streamlines reduced air resistance in vehicles
- low resistance wires reduce heat loss
