Energy Flashcards
What is kinetic energy?
Energy stored by movement
What is gravitational potential energy?
Energy stored in objects raised above the Earth’s surface - exists because of the Earth’s gravitational field
What is chemical energy?
Energy stored by chemical bonds between atoms
What is elastic potential energy?
Energy stored by stretching or compressing an object
Equation for kinetic energy
Kinetic energy = 1/2 mass x velocity^2
E = 1/2 mv^2
Equation for gravitational potential energy
Gravitational potential energy = mass x gravitational field strength x height
E = mgh
Equation for elastic potential energy
Elastic potential energy = 1/2 spring constant x extension^2
E = 1/2 ke^2
What is specific heat capacity?
Energy needed to raise temperature of 1 KG by 1℃
Equation for change in thermal energy (specific heat capacity)
Change in thermal energy = mass x specific heat capacity x change in temperature
∆E =mc∆T
Required Practical 1: Specific heat capacity
- Measure mass of object
- Heat it up for 2 minutes
- Work out energy from power and time
- Work out specific heat capacity
Energy transfer of arrow shot from top of city wall
Gravitational potential → mostly kinetic + a bit of thermal
What happens when work is done on an object?
Energy is transferred to the object
Energy transfer of a racing driver starting their car
Then when they crash because the other driver went the wrong way
Chemical → kinetic + sound + thermal
Kinetic → lots of sound + thermal + potential (both cars)
What is efficiency?
How good a device is at transferring energy input to useful energy - if energy is wasted then it is dissipated in useless ways, e.g. sound or thermal energy, but if it is used for the intended purpose it is useful
Equation for efficiency
Efficiency = Useful energy/power output ÷ total energy/power input x 100
What is power?
Rate of work done or energy transferred
Equation for power
Power = work done/energy transferred ÷ time P = E/t
Insulation in a house
- Thicker walls, use material with low thermal conductivity
- Cavity wall insulation - air gap between walls filled with foam which has trapped air, prevents convection
- Double glazing - 2 layers of glass with air gap too small for air circulation, prevents convection
- Fit carpets to reduce heat loss from floors
Required Practical 2: Thermal Insulation
- Boil water
- Pour into beaker with 0 layers of newspaper (control)
- Measure temperature, repeat every 5 minutes
- Do again with different layers of newspaper
- Plot cooling curve graph - more insulation should mean slower cooling
- Repeat whole experiment but changing material for insulation this time
What are renewable and non-renewable energy resources?
Non-renewable energy resources will eventually run out
Renewable energy resources will not run out
Hydroelectric
Generators in dams use moving water to drive turbines
Advantages:
• Renewable
• No gas emissions
• Cheap to run
Disadvantages:
• Initially expensive
• Limited suitable locations - needs enough water and land to create a reservoir
• Floods animal habitats and farmland
Wind
Uses kinetic energy of wind to turn a turbine Advantages: • Renewable • No gas emissions • No fuel costs
Disadvantages:
• Low power output from each turbine
• Unreliable – they only work when it is windy
• Visual pollution for some
Solar
Solar (photovoltaic) cells convert sunlight to electricity
Advantages:
• Renewable
• No gas emissions
• No fuel costs
Disadvantages:
• Expensive to produce the panels
• Low power output
• Unreliable supply – they do not work at night
Geothermal
Uses underground rocks (heated up by lava) to heat up water into steam which turns a turbine
Advantages:
• Renewable
• No gas emissions
• No fuel costs
Disadvantages:
• Expensive to build
• Limited suitable locations - needs hot rocks near the surface
Wave and tidal
Uses motion of waves in the sea or the movement of tides to turn turbines
Advantages:
• Renewable
• No gas emissions
• No fuel costs
Disadvantages:
• Limited suitable locations - coastal areas only
• Installing turbines and generators interferes with other activities (fishing, swimming etc.) and/or wildlife
Biofuel
Uses heat from burning biofuels (from (recently) living organisms) to heat water into steam which turns a turbine
Advantages:
• Renewable
• Suitable for remote/rural locations
• Carbon neutral - the carbon used by the organism when it was living equals the carbon released when it is burned
Disadvantages:
• Biofuels release carbon dioxide when burned.
• Low power output – only suitable for small scale use
Fossil fuels
Uses heat from burning coal, oil or gas to heat water into steam which turns a turbine
Advantages:
• High power output
Disadvantages:
• Non-renewable
• Carbon dioxide, sulfur dioxide and nitrogen oxides released into the atmosphere when burned
• Oil spills are environmental disasters (oil only)
Nuclear
Uses nuclear fission releases energy to heat water into steam which turns a turbine
Advantages:
• No waste gases produced
• Large power output from a small amount of fuel
Disadvantages:
• Radioactive waste produced
• Power stations expensive to build and decommission
• Nuclear meltdowns
